Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus ( 1 ) is capable of performing a refrigeration cycle using a small-GWP refrigerant. The refrigeration cycle apparatus ( 1 ) includes a refrigerant circuit ( 10 ) and a refrigerant enclosed in the refrigerant circuit ( 10 ). The refrigerant circuit includes a compressor ( 21 ), a condenser ( 23 ), a decompressing section ( 24 ), and an evaporator ( 31 ). The refrigerant contains at least 1,2-difluoroethylene.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus.

BACKGROUND ART

In the related art, R410A has been frequently used as a refrigerant in refrigeration cycle apparatuses such as air conditioners. R410A is a two-component mixed refrigerant of difluoromethane (CH₂F₂; HFC-32 or R32) and pentafluoroethane (C₂HF₅; HFC-125 or R125), which is a pseudo-azeotropic composition.

However, R410A has a global warming potential (GWP) of 2088. From the viewpoint of increasing concern for global warming, R32 having a lower GWP has been more frequently used in recent years.

Therefore, for example, PTL 1 (International Publication No. 2015/141678) proposes various low-GWP mixture refrigerants as alternatives to R410A.

SUMMARY OF THE INVENTION (1) First Group

It has not been studied that good lubricity in a refrigeration cycle apparatus is achieved when a refrigeration cycle is performed using a refrigerant having a sufficiently low GWP.

In view of the foregoing, it is an object of the present disclosure to provide a refrigeration cycle apparatus in which good lubricity can be achieved when a refrigeration cycle is performed using a refrigerant having a sufficiently low GWP.

A refrigeration cycle apparatus according to a first aspect of first group comprises a working fluid for a refrigerating machine that contains a refrigerant composition containing a refrigerant and that contains a refrigerating oil. The refrigerant comprises trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and 2,3,3,3-tetrafluoro-1-propene (R1234yf).

Since this refrigeration cycle apparatus contains a refrigerant having a sufficiently low GWP and a refrigerating oil, good lubricity in the refrigeration cycle apparatus can be achieved when a refrigeration cycle is performed using the above refrigerant composition. In this refrigeration cycle, good lubricity in the refrigeration cycle apparatus can also be achieved when a refrigerant having a refrigeration capacity (may also be referred to as a cooling capacity or a capacity) and a coefficient of performance (COP) equal to those of R410A is used.

A refrigeration cycle apparatus according to a second aspect of first group is the refrigeration cycle apparatus according to the first aspect of first group, wherein the refrigerating oil has a kinematic viscosity at 40° C. of 1 mm²/s or more and 750 mm²/s or less.

A refrigeration cycle apparatus according to a third aspect of first group is the refrigeration cycle apparatus according to the first aspect or the second aspect of first group, wherein the refrigerating oil has a kinematic viscosity at 100° C. of 1 mm²/s or more and 100 mm²/s or less.

A refrigeration cycle apparatus according to a fourth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the third aspect of first group, wherein the refrigerating oil has a volume resistivity at 25° C. of 1.0×10¹²Ω·cm or more.

A refrigeration cycle apparatus according to a fifth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the fourth aspect of first group, wherein the refrigerating oil has an acid number of 0.1 mgKOH/g or less.

A refrigeration cycle apparatus according to a sixth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the fifth aspect of first group, wherein the refrigerating oil has an ash content of 100 ppm or less.

A refrigeration cycle apparatus according to a seventh aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the sixth aspect of first group, wherein the refrigerating oil has an aniline point of −100° C. or higher and 0° C. or lower.

A refrigeration cycle apparatus according to an eighth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the seventh aspect of first group and includes a refrigerant circuit. The refrigerant circuit includes a compressor, a condenser, a decompressing unit, and an evaporator connected to each other through a refrigerant pipe. The working fluid for a refrigerating machine circulates through the refrigerant circuit.

A refrigeration cycle apparatus according to a ninth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the eighth aspect of first group, wherein a content of the refrigerating oil in the working fluid for a refrigerating machine is 5 mass % or more and 60 mass % or less.

A refrigeration cycle apparatus according to a tenth aspect of first group is the refrigeration cycle apparatus according to any one of the first aspect to the ninth aspect of first group, wherein the refrigerating oil contains at least one additive selected from an acid scavenger, an extreme pressure agent, an antioxidant, an antifoaming agent, an oiliness improver, a metal deactivator, an anti-wear agent, and a compatibilizer. A content of the additive is 5 mass % or less relative to a mass of the refrigerating oil containing the additive.

(3) Third Group

A specific refrigerant circuit that can use such a small-GWP refrigerant has not been studied at all.

A refrigeration cycle apparatus according to a first aspect of third group includes a refrigerant circuit and a refrigerant. The refrigerant circuit includes a compressor, a condenser, a decompressing section, and an evaporator. The refrigerant contains at least 1,2-difluoroethylene. The refrigerant is enclosed in the refrigerant circuit.

Since the refrigeration cycle apparatus can perform a refrigeration cycle using the refrigerant containing 1,2-difluoroethylene in the refrigerant circuit including the compressor, the condenser, the decompressing section, and the evaporator, the refrigeration cycle apparatus can perform a refrigeration cycle using a small-GWP refrigerant.

A refrigeration cycle apparatus according to a second aspect of third group is the refrigeration cycle apparatus according to the first aspect of third group, in which the refrigerant circuit further includes a low-pressure receiver. The low-pressure receiver is provided midway in a refrigerant flow path extending from the evaporator toward a suction side of the compressor.

The refrigeration cycle apparatus can perform a refrigeration cycle while the low-pressure receiver stores an excessive refrigerant in the refrigerant circuit.

A refrigeration cycle apparatus according to a third aspect of third group is the refrigeration cycle apparatus according to the first aspect or the second aspect of third group, in which the refrigerant circuit further includes a high-pressure receiver. The high-pressure receiver is provided midway in a refrigerant flow path extending from the condenser toward the evaporator.

The refrigeration cycle apparatus can perform a refrigeration cycle while the high-pressure receiver stores an excessive refrigerant in the refrigerant circuit.

A refrigeration cycle apparatus according to a fourth aspect of third group is the refrigeration cycle apparatus according to any one of the first aspect to the third aspect of third group, in which the refrigerant circuit further includes a first decompressing section, a second decompressing section, and an intermediate-pressure receiver. The first decompressing section, the second decompressing section, and the intermediate-pressure receiver are provided midway in a refrigerant flow path extending from the condenser toward the evaporator. The intermediate-pressure receiver is provided between the first decompressing section and the second decompressing section in the refrigerant flow path extending from the condenser toward the evaporator.

The refrigeration cycle apparatus can perform a refrigeration cycle while the intermediate-pressure receiver stores an excessive refrigerant in the refrigerant circuit.

A refrigeration cycle apparatus according to a fifth aspect of third group is the refrigeration cycle apparatus according to any one of the first aspect to the fourth aspect of third group, in which the refrigeration cycle apparatus further includes a control unit. The refrigerant circuit further includes a first decompressing section and a second decompressing section. The first decompressing section and the second decompressing section are provided midway in a refrigerant flow path extending from the condenser toward the evaporator. The control unit adjusts both a degree of decompression of a refrigerant passing through the first decompressing section and a degree of decompression of a refrigerant passing through the second decompressing section.

The refrigeration cycle apparatus, by controlling the respective degrees of decompression of the first decompressing section and the second decompressing section provided midway in the refrigerant flow path extending from the condenser toward the evaporator, can decrease the concentration of the refrigerant located between the first decompressing section and the second decompressing section provided midway in the refrigerant flow path extending from the condenser toward the evaporator. Thus, the refrigerant enclosed in the refrigerant circuit is likely present more in the condenser and/or the evaporator, thereby improving the capacity.

A refrigeration cycle apparatus according to a sixth aspect of third group is the refrigeration cycle apparatus according to any one of the first aspect to the fifth aspect of third group, in which the refrigerant circuit further includes a refrigerant heat exchanging section. The refrigerant heat exchanging section causes a refrigerant flowing from the condenser toward the evaporator and a refrigerant flowing from the evaporator toward the compressor to exchange heat with each other.

With the refrigeration cycle apparatus, in the refrigerant heat exchanging section, the refrigerant flowing from the evaporator toward the compressor is heated with the refrigerant flowing from the condenser toward the evaporator. Thus, liquid compression by the compressor can be controlled.

(13) Thirteenth Group

In recent years, use of refrigerant with a low GWP (hereinafter referred to as low-GWP refrigerant) in air conditioners has been considered from the viewpoint of environmental protection. A dominant example of low-GWP refrigerant is a refrigerant mixture containing 1,2-difluoroethylene.

However, the related art giving consideration from the aspect of increasing the efficiency of air conditioners using the foregoing refrigerant is rarely found. For example, in the case of applying the foregoing refrigerant to the air conditioner disclosed in PTL 1 (Japanese Unexamined Patent Application Publication No. 2013-124848), there is an issue of how to achieve high efficiency.

An air conditioner according to a first aspect of thirteenth group includes a compressor that compresses a refrigerant mixture containing at least 1,2-difluoroethylene, a motor that drives the compressor, and a power conversion device. The power conversion device is connected between an alternating-current (AC) power source and the motor, has a switching element, and controls the switching element such that an output of the motor becomes a target value.

In the air conditioner that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the motor rotation rate of the compressor can be changed in accordance with an air conditioning load, and thus a high annual performance factor (APF) can be achieved.

An air conditioner according to a second aspect of thirteenth group is the air conditioner according to the first aspect of thirteenth group, in which the power conversion device includes a rectifier circuit and a capacitor. The rectifier circuit rectifies an AC voltage of the AC power source. The capacitor is connected in parallel to an output side of the rectifier circuit and smooths voltage variation caused by switching in the power conversion device.

In this air conditioner, an electrolytic capacitor is not required on the output side of the rectifier circuit, and thus an increase in the size and cost of the circuit is suppressed.

An air conditioner according to a third aspect of thirteenth group is the air conditioner according to the first aspect or the second aspect of thirteenth group, in which the AC power source is a single-phase power source.

An air conditioner according to a fourth aspect of thirteenth group is the air conditioner according to the first aspect or the second aspect of thirteenth group, in which the AC power source is a three-phase power source.

An air conditioner according to a fifth aspect of thirteenth group is the air conditioner according to the first aspect of thirteenth group, in which the power conversion device is an indirect matrix converter including a converter and an inverter. The converter converts an AC voltage of the AC power source into a direct-current (DC) voltage. The inverter converts the DC voltage into an AC voltage and supplies the AC voltage to the motor.

This air conditioner is highly efficient and does not require an electrolytic capacitor on the output side of the rectifier circuit, and thus an increase in the size and cost of the circuit is suppressed.

An air conditioner according to a sixth aspect of thirteenth group is the air conditioner according to the first aspect of thirteenth group, in which the power conversion device is a matrix converter that directly converts an AC voltage of the AC power source into an AC voltage having a predetermined frequency and supplies the AC voltage having the predetermined frequency to the motor.

This air conditioner is highly efficient and does not require an electrolytic capacitor on the output side of the rectifier circuit, and thus an increase in the size and cost of the circuit is suppressed.

An air conditioner according to a seventh aspect of thirteenth group is the air conditioner according to the first aspect of thirteenth group, in which the compressor is any one of a scroll compressor, a rotary compressor, a turbo compressor, and a screw compressor.

An air conditioner according to an eighth aspect of thirteenth group is the air conditioner according to any one of the first aspect to the seventh aspect of thirteenth group, in which the motor is a permanent magnet synchronous motor having a rotor including a permanent magnet.

(14) Fourteenth Group

In recent years, use of refrigerant with a low GWP (hereinafter referred to as low-GWP refrigerant) in air conditioners has been considered from the viewpoint of environmental protection. A dominant example of low-GWP refrigerant is a refrigerant mixture containing 1,2-difluoroethylene.

However, the related art giving consideration from the aspect of increasing the efficiency of air conditioners using the foregoing refrigerant is rarely found. In the case of applying the foregoing refrigerant to the air conditioner, there is an issue of how to achieve high efficiency.

An air conditioner according to a first aspect of fourteenth group includes a compressor that compresses a refrigerant mixture containing at least 1,2-difluoroethylene, a motor that drives the compressor, and a connection unit that causes power to be supplied from an alternating-current (AC) power source to the motor without frequency conversion.

In the air conditioner that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the compressor can be driven without interposing a power conversion device between the AC power source and the motor. Thus, it is possible to provide the air conditioner that is environmentally friendly and has a relatively inexpensive configuration.

An air conditioner according to a second aspect of fourteenth group is the air conditioner according to the first aspect of fourteenth group, in which the connection unit directly applies an AC voltage of the AC power source between at least two terminals of the motor.

An air conditioner according to a third aspect of fourteenth group is the air conditioner according to the first aspect or the second aspect of fourteenth group, in which the AC power source is a single-phase power source.

An air conditioner according to a fourth aspect of fourteenth group is the air conditioner according to any one of the first aspect to the third aspect of fourteenth group, in which one terminal of the motor is connected in series to an activation circuit.

An air conditioner according to a fifth aspect of fourteenth group is the air conditioner according to the fourth aspect of fourteenth group, in which the activation circuit is a circuit in which a positive temperature coefficient thermistor and an operation capacitor are connected in parallel to each other.

In the air conditioner that uses a refrigerant mixture containing at least 1,2-difluoroethylene, after the compressor has been activated, the PTC thermistor self-heats and the resistance value thereof increases, and switching to an operation circuit substantially by the operation capacitor occurs. Thus, the compressor enters a state of being capable of outputting a rated torque at appropriate timing.

An air conditioner according to a sixth aspect of fourteenth group is the air conditioner according to the first aspect or the second aspect of fourteenth group, in which the AC power source is a three-phase power source.

This air conditioner does not require an activation circuit and thus the cost is relatively low.

An air conditioner according to a seventh aspect of fourteenth group is the air conditioner according to any one of the first aspect to the sixth aspect of fourteenth group, in which the motor is an induction motor.

In this air conditioner, the motor is capable of high output with relatively low cost, and thus the efficiency of the air conditioner can be increased.

(15) Fifteenth Group

There has been widely used a warm-water generating apparatus that generates warm water by a boiler or an electric heater. In addition, there is also a warm-water generating apparatus that employs a heat pump unit as a heat source.

A conventional warm-water generating apparatus that employs a heat pump unit frequently uses carbon dioxide as a refrigerant in the heat pump unit. However, there is a demand for generating warm water more efficiently as compared to the conventional warm-water generating apparatus.

A warm-water generating apparatus according to a first aspect of fifteenth group uses, as a refrigerant, a mixed refrigerant containing at least 1,2-difluoroethylene (HFO-1132(E)). The warm-water generating apparatus includes a compressor, a heat-source-side first heat exchanger, an expansion mechanism, and a use-side second heat exchanger. The second heat exchanger causes the mixed refrigerant flowing therein and first water to exchange heat with each other to heat the first water.

The warm-water generating apparatus uses, as the refrigerant, the above-described mixed refrigerant instead of carbon dioxide which has been frequently used. Accordingly, warm water can be efficiently generated.

A warm-water generating apparatus according to a second aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a tank and a circulation flow path. A circulation flow path allows the first water to circulate between the tank and the second heat exchanger.

A warm-water generating apparatus according to a third aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a first circulation flow path, a second circulation flow path, a third heat exchanger, and a tank. The first circulation flow path allows the first water heated by the second heat exchanger to circulate. The second circulation flow path is different from the first circulation flow path. The third heat exchanger causes the first water flowing through the first circulation flow path and second water flowing through the second circulation flow path to exchange heat with each other to heat the second water flowing through the second circulation flow path. The tank stores the second water heated by the third heat exchanger.

A warm-water generating apparatus according to a fourth aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a first circulation flow path and a tank. The first circulation flow path allows the first water heated by the second heat exchanger to circulate. A portion of the first circulation flow path is disposed in the tank and allows the first water flowing through the first circulation flow path and second water in the tank to exchange heat with each other to heat the second water in the tank.

A warm-water generating apparatus according to a fifth aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a tank, a first circulation flow path, a third heat exchanger, a second circulation flow path, and a third flow path. The first circulation flow path allows the first water to circulate between the second heat exchanger and the tank. The second circulation flow path allows the first water to circulate between the third heat exchanger and the tank. The third flow path is different from the first circulation flow path and the second circulation flow path. The third heat exchanger causes the first water flowing from the tank and third water flowing through the third flow path to exchange heat with each other to heat the third water flowing through the third flow path.

A warm-water generating apparatus according to a sixth aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a tank, a first circulation flow path, and a second flow path. The first circulation flow path allows the first water to circulate between the tank and the second heat exchanger. The second flow path is different from the first circulation flow path. A portion of the second flow path is disposed in the tank and allows the first water in the tank and second water flowing through the second flow path to exchange heat with each other to heat the second water flowing through the second flow path.

A warm-water generating apparatus according to a seventh aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a tank that stores the first water and a flow path through which second water flows. A portion of the flow path is disposed in the tank. The second heat exchanger heats, in the tank, the first water stored in the tank. The first water stored in the tank heats the second water flowing through the flow path.

A warm-water generating apparatus according to an eighth aspect of fifteenth group is the warm-water generating apparatus according to the first aspect of fifteenth group, and further includes a tank and a flow path through which the first water flows from a water supply source to the tank. The second heat exchanger heats the first water flowing through the flow path.

A warm-water generating apparatus according to a ninth aspect of fifteenth group is the warm-water generating apparatus according to any one of the first aspect to the eighth aspect of fifteenth group, and further includes a use-side fourth heat exchanger and a fourth circulation flow path. The fourth heat exchanger is a heat exchanger that is different from the second heat exchanger. In the fourth circulation flow path, fourth water for cooling or heating flows. The fourth heat exchanger causes the mixed refrigerant flowing therein and the fourth water flowing through the fourth circulation flow path to exchange heat with each other to cool or heat the fourth water.

(17) Seventeenth Group

Hitherto, as an air conditioning apparatus that air-conditions a plurality of rooms in an interior by one air conditioning apparatus, a multi-type air conditioning apparatus has been known.

A multi-type air conditioning apparatus such as the multi-type air conditioning apparatus includes a first indoor unit and a second indoor unit that are disposed in different rooms. In such an air conditioning apparatus, since a refrigerant is caused to circulate in the first indoor unit and the second indoor unit, the amount of refrigerant with which the air conditioning apparatus is filled is large.

An air conditioning apparatus that air-conditions a plurality of rooms in an interior has a problem in that the amount of refrigerant with which the air conditioning apparatus needs to be reduced.

An air conditioning apparatus according to a first aspect of seventeenth group includes a compressor, a use-side heat exchanger that exchanges heat with first air, a heat-source-side heat exchanger that exchanges heat with second air, a refrigerant that contains at least 1,2-difluoroethylene and that circulates in the compressor, the use-side heat exchanger, and the heat-source-side heat exchanger to repeat a refrigeration cycle, a first duct that supplies the first air to a plurality of rooms in an interior, and a casing that includes a use-side space that is connected to the first duct and that accommodates the use-side heat exchanger, the casing being configured to allow the first air after heat exchange with the refrigerant at the use-side heat exchanger to be sent out to the first duct.

Since the number of indoor-side heat exchangers of this air conditioning apparatus is smaller than the number of indoor-side heat exchangers of air conditioning apparatus in which a plurality of indoor units are disposed in a plurality of rooms, it is possible to reduce the amount of refrigerant with which the air conditioning apparatus is filled.

An air conditioning apparatus according to a second aspect of seventeenth group is the air conditioning apparatus of the first aspect of seventeenth group and includes a second duct that introduces the first air from the interior, a use-side unit that includes the casing and that is configured to guide the first air introduced from the interior to the use-side heat exchanger with the casing connected to the second duct, and a heat-source-side unit that accommodates the heat-source-side heat exchanger and that differs from the use-side unit.

In the air conditioning apparatus, since the use-side unit and the heat-source-side unit are different units, the air conditioning apparatus is easily installed.

An air conditioning apparatus according to a third aspect of seventeenth group is the air conditioning apparatus of the first aspect of seventeenth group and includes a third duct that introduces the first air from an exterior, a use-side unit that includes the casing and that is configured to guide the first air introduced from the exterior to the use-side heat exchanger with the casing connected to the third duct, and a heat-source-side unit that accommodates the heat-source-side heat exchanger and that differs from the use-side unit.

In the air conditioning apparatus, since the use-side unit and the heat-source-side unit are different units, the air conditioning apparatus is easily installed.

An air conditioning apparatus according to a fourth aspect of seventeenth group is the air conditioning apparatus of the first aspect of seventeenth group and includes a second duct that is connected to the casing and that supplies the first air introduced from the interior to the use-side space, wherein the casing is provided with a partition plate that partitions the casing into a heat-source-side space through which the second air introduced from an exterior passes and the use-side space to prevent circulation of air in the heat-source-side space and the use-side space, and wherein the heat-source-side heat exchanger is disposed in the heat-source-side space.

In the air conditioning apparatus, since, in one casing, the use-side heat exchanger and the heat-source-side heat exchanger are accommodated in the use-side space and the heat-source-side space that are separated by the partition plate in the same casing, the air conditioning apparatus is easily installed by using a limited space.

(22) Twenty-Second Group

Configurations of refrigerant circuits that realize highly efficient operation by using a refrigerant having a low global warming potential have not been fully proposed.

A refrigeration cycle apparatus according to a first aspect of twenty-second group includes a refrigerant circuit including a compressor, a heat source-side heat exchanger, an expansion mechanism, and a usage-side heat exchanger. In the refrigerant circuit, a refrigerant containing at least 1,2-difluoroethylene (HFO-1132 (E)) is sealed. At least during a predetermined operation, in at least one of the heat source-side heat exchanger and the usage-side heat exchanger, a flow of the refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows.

The refrigeration cycle apparatus according to the first aspect of twenty-second group realizes highly efficient operation effectively utilizing a heat exchanger, by using the refrigerant that contains 1,2-difluoroethylene (HFO-1132(E)) and that has a low global warming potential.

A refrigeration cycle apparatus according to a second aspect of twenty-second group is the refrigeration cycle apparatus of the first aspect of twenty-second group, and, during an operation of the refrigeration cycle apparatus using the heat source-side heat exchanger as an evaporator, in the heat source-side heat exchanger, a flow of the refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows.

A refrigeration cycle apparatus according to a third aspect of twenty-second group is the refrigeration cycle apparatus of the first aspect or the second aspect of twenty-second group, and, during an operation of the refrigeration cycle apparatus using the heat source-side heat exchanger as a condenser, in the heat source-side heat exchanger, a flow of the refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows.

Here, even when a refrigerant is used, with which a temperature difference between the refrigerant and the heating medium is difficult to be generated on an exit side of the condenser due to influence of temperature glide, the temperature difference is relatively easily ensured from an entrance to the exit of the condenser, and efficient operation of the refrigeration cycle apparatus can be realized.

A refrigeration cycle apparatus according to a fourth aspect of twenty-second group is the refrigeration cycle apparatus of any one of the first to third aspects of twenty-second group, and, during an operation of the refrigeration cycle apparatus using the usage-side heat exchanger as an evaporator, in the usage-side heat exchanger, a flow of the refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows.

A refrigeration cycle apparatus according to a fifth aspect of twenty-second group is the refrigeration cycle apparatus of any one of the first to fourth aspects of twenty-second group, and, during an operation of the refrigeration cycle apparatus using the usage-side heat exchanger as a condenser, in the usage-side heat exchanger, a flow of the refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows.

A refrigeration cycle apparatus according to a sixth aspect of twenty-second group is the refrigeration cycle apparatus of any one of the first to fifth aspects of twenty-second group, and the heating medium is air.

A refrigeration cycle apparatus according to a seventh aspect of twenty-second group is the refrigeration cycle apparatus of any one of the first to fifth aspects of twenty-second group, and the heating medium is a liquid.

(25) Embodiment of Twenty-Fifth Group

A refrigeration apparatus known in the art includes a high-temperature-side (primary-side) refrigeration cycle and a low-temperature-side (secondary-side) refrigeration cycle. For example, there is a two-stage refrigeration apparatus in which an HFC refrigerant (e.g., R410A and R32) or an HFO refrigerant is used as refrigerant for the high-temperature-side refrigeration cycle and a carbon dioxide refrigerant is used as refrigerant for the low-temperature-side refrigeration cycle.

Such a two-stage refrigeration apparatus in which two cycles are used in combination is in need of improvement in operational efficiency.

A refrigeration apparatus according to a first aspect of twenty-fifth group includes a first cycle and a second cycle. The first cycle includes a first compressor, a first radiator, a first expansion mechanism, and a first heat absorber that are arranged in such a manner as to be connected to the first cycle. A first refrigerant circulates through the first cycle. The second cycle includes a second radiator and a second heat absorber that are arranged in such a manner as to be connected to the second cycle. A second refrigerant circulates through the second cycle. The first heat absorber and the second radiator constitute a heat exchanger. In the heat exchanger, heat is exchanged between the first refrigerant flowing through the first heat absorber and the second radiator refrigerant through the second radiator. At least one of the first refrigerant and the second refrigerant is a refrigerant mixture containing at least 1,2-difluoroethylene (HFO-1132(E)).

The efficiency of heat exchange in the heat exchanger may be enhanced through the use of the refrigerant mixture.

A refrigeration apparatus according to a second aspect of twenty-fifth group includes a first cycle and a second cycle. The first cycle includes a first compressor, a first radiator, a first expansion mechanism, and a first heat absorber that are arranged in such a manner as to be connected to the first cycle. A first refrigerant circulates through the first cycle. The second cycle includes a second radiator and a second heat absorber that are arranged in such a manner as to be connected to the second cycle. A second refrigerant circulates through the second cycle. The first radiator and the second heat absorber constitute a heat exchanger. In the heat exchanger, heat is exchanged between the first refrigerant flowing through the first radiator and the second refrigerant flowing through the second heat absorber. At least one of the first refrigerant and the second refrigerant is a refrigerant mixture containing at least 1,2-difluoroethylene (HFO-1132(E)).

The efficiency of heat exchange in the heat exchanger may be enhanced through the use of the refrigerant mixture.

A refrigeration apparatus according to a third aspect of twenty-fifth group is the refrigeration apparatus according to the first aspect of twenty-fifth group in which the second cycle further includes a second compressor and a second expansion mechanism that are arranged in such a manner as to be connected to the second cycle. The first refrigerant flowing through the first radiator of the first cycle releases heat into outside air. The first refrigerant is the refrigerant mixture. The second refrigerant is carbon dioxide.

A refrigeration apparatus according to a fourth aspect of twenty-fifth group is the refrigeration apparatus according to the first aspect of twenty-fifth group in which the second cycle further includes a second compressor and a second expansion mechanism that are arranged in such a manner as to be connected to the second cycle. The first refrigerant flowing through the first radiator of the first cycle releases heat into outside air. The first refrigerant is the refrigerant mixture. The second refrigerant is the refrigerant mixture.

A refrigeration apparatus according to a fifth aspect of twenty-fifth group is the refrigeration apparatus according to the first aspect of twenty-fifth group in which the second cycle further includes a second compressor and a second expansion mechanism that are arranged in such a manner as to be connected to the second cycle. The first refrigerant flowing through the first radiator of the first cycle releases heat into outside air. The first refrigerant is R32. The second refrigerant is the refrigerant mixture.

A refrigeration apparatus according to a sixth aspect of twenty-fifth group is the refrigeration apparatus according to the first aspect of twenty-fifth group in which the first refrigerant flowing through the first radiator of the first cycle releases heat into outside air. The first refrigerant is the refrigerant mixture. The second refrigerant is a liquid medium.

A refrigeration apparatus according to a seventh aspect of twenty-fifth group is the refrigeration apparatus according to the second aspect of twenty-fifth group in which the second cycle further includes a second compressor and a second expansion mechanism that are arranged in such a manner as to be connected to the second cycle. The first refrigerant flowing through the first heat absorber of the first cycle takes away heat from outside air. The first refrigerant is the refrigerant mixture. The second refrigerant is a refrigerant whose saturation pressure at a predetermined temperature is lower than a saturation pressure of the refrigerant mixture at the predetermined temperature.

(26) Detail of Refrigerant for Each of Groups

Each of 1st to 25th groups uses the refrigerant according to a first aspect that contains at least 1,2-difluoroethylene.

Preferably, each of techniques of 1st to 25th groups uses a refrigerant A, B, C or D as follows.

(26-1) the Refrigerant A

The refrigerant A according to a second aspect comprises trans-1,2-difluoroethylene (HFO-1132 (E)), trifluoroethylene (HFO-1123), and 2,3,3,3-tetrafluoro-1-propene (R1234yf).

The refrigerant A according to a third aspect is the refrigerant according to the second aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments OD, DG, GH, and HO that connect the following 4 points:

point D (87.6, 0.0, 12.4), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DG, and GH (excluding the points O and H);

the line segment DG is represented by coordinates

(0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment GH is represented by coordinates

(−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and

the line segments HO and OD are straight lines.

The refrigerant A according to a fourth aspect is the refrigerant according to the second aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments LG, GH, HI, and IL that connect the following 4 points.

point L (72.5, 10.2, 17.3), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point I (72.5, 27.5, 0.0), or on the line segments LG, GH, and IL (excluding the points H and I);

the line segment LG is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment GH is represented by coordinates (−0.0134z−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and

the line segments HI and IL are straight lines.

The refrigerant A according to a fifth aspect is the refrigerant according to any one of the second aspect to fourth aspect, further comprising difluoromethane (R32).

The refrigerant A according to a sixth aspect is the refrigerant according to the fifth aspect, wherein

when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum in the refrigerant is respectively represented by x, y, z, and a,

if <a≤10.0, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.02a²−2.46a+93.4, 0, −0.02a²+2.46a+6.6), point B′ (−0.008a²−1.38a+56, 0.018a²−0.53a+26.3, −0.01a²+1.91a+17.7), point C (−0.016a²+1.02a+77.6, 0.016a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point O and point C);

if 10.0<a≤16.5, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0244a²−2.5695a+94.056, 0, −0.0244a²+2.5695a+5.944), point B′ (0.1161a²−1.9959a+59.749, 0.014a²−0.3399a+24.8, −0.1301a²+2.3358a+15.451), point C (−0.0161a²+1.02a+77.6, 0.0161a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point C and point C); or

if 16.5<a≤21.8, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0161a²−2.3535a+92.742, 0, −0.0161a²+2.3535a+7.258), point B′ (−0.0435a²−0.0435a+50.406, −0.0304a²+1.8991a−0.0661, 0.0739a²−1.8556a+49.6601), point C (−0.0161a²+0.9959a+77.851, 0.0161a²−0.9959a+22.149, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point O and point C).

(26-2) the Refrigerant B

The refrigerant B according to a seventh aspect,

the refrigerant comprising HFO-1132(E) and HFO-1123 in a total amount of 99.5 mass % or more based on the entire refrigerant B according to a seventh aspect, and

the refrigerant comprising 62.5 mass % to 72.5 mass % of HFO-1132(E) based on the entire refrigerant B according to a seventh aspect.

(26-3) the Refrigerant C

The refrigerant C according to a eighth aspect is the refrigerant comprising HFO-1132(E), R32, and R1234yf.

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AC, CF, FD, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point C (36.5, 18.2, 45.3), point F (47.6, 18.3, 34.1), and point D (72.0, 0.0, 28.0), or on these line segments;

the line segment AC is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+28.904),

the line segment FD is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and

the line segments CF and DA are straight lines.

The refrigerant C according to a ninth aspect is the refrigerant comprising HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AB, BE. ED, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point B (42.6, 14.5, 42.9), point E (51.4, 14.6, 34.0), and point D (72.0, 0.0, 28.0), or on these line segments;

the line segment AB is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+280.904),

the line segment ED is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and

the line segments BE and DA are straight lines.

The refrigerant C according to a tenth aspect is the refrigerant comprising HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GI, IJ, and JG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point I (55.1, 18.3, 26.6), and point J (77.5, 18.4, 4.1), or on these line segments;

the line segment GI is represented by coordinates (0.02y²−2.4583y+93.396, y, −0.02y²+1.4583y+6.604), and

the line segments IJ and JG are straight lines.

The refrigerant C according to a eleventh aspect is the refrigerant comprising HFO-1132(E), R32, and R1234yf,

wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GH, HK, and KG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point H (61.8, 14.6, 23.6), and point K (77.5, 14.6, 7.9), or on these line segments;

the line segment GH is represented by coordinates (0.02y²−2.4583y+93.3%, y, −0.02y²+1.4583y+6.604), and

the line segments HK and KG are straight lines.

(26-4) the Refrigerant D

The refrigerant D according to a twelfth aspect is the refrigerant comprising HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′E′, E′A′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C′(56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), point E′ (41.8, 39.8, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments C′D′, D′E′, and E′A′ (excluding the points C′ and A′);

the line segment C′D′ is represented by coordinates

(−0.0297z²−0.1915z+56.7, 0.0297z²+1.1915z+43.3, z),

the line segment D′E′ is represented by coordinates

(−0.0535z²+0.3229z+53.957, 0.0535z²+0.6771z+46.043, z), and

the line segments OC′, E′A′, and A′O are straight lines.

The refrigerant D according to a thirteenth aspect is the refrigerant comprising HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, v, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC, CD, DE, EA′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), point E (72.2, 9.4, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments CD, DE, and EA′ (excluding the points C and A′);

the line segment CDE is represented by coordinates

(−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and

the line segments OC, EA′, and A′O are straight lines.

The refrigerant D according to a fourteenth aspect is the refrigerant comprising HFO-1132(E). HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′A, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments C′D′ and D′A (excluding the points C′ and A);

the line segment C′D′ is represented by coordinates

(−0.0297z²−0.1915z+56.7, 0.0297z²+1.1915z+43.3, z), and

the line segments OC′. D′A, and AO are straight lines.

The refrigerant D according to a fifteenth aspect is the refrigerant comprising HFO-1132(E), HFO-1123, and R32,

wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC, CD, DA, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments CD and DA (excluding the points C and A);

the line segment CD is represented by coordinates

(−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and

the line segments OC, DA, and AO are straight lines.

(27) Features of Each Group Using One of Refrigerants Noted Above

According to the technique of first group using any one of refrigerants having a sufficiently low GWP above, good lubricity in the refrigeration cycle apparatus can be achieved.

According to the technique of second group using any one of refrigerants having a sufficiently low GWP above, good lubricity can be achieved when a refrigeration cycle is performed.

According to the technique of third group using any one of refrigerants having a sufficiently low GWP above, a refrigeration cycle can be performed.

According to the technique of fourth group using any one of refrigerants having a sufficiently low GWP above, a refrigerant reaching electric components is reduced if the refrigerant leaks.

According to the technique of fifth group using any one of refrigerants having a sufficiently low GWP above, the operation efficiency of a refrigeration cycle can be improved.

According to the technique of sixth group using any one of refrigerants having a sufficiently low GWP above, damage to the connection pipe can be reduced.

According to the technique of seventh group using any one of refrigerants having a sufficiently low GWP above, if the above-described refrigerant leaks, ignition at the electric heater can be suppressed.

According to the technique of eighth group using any one of refrigerants having a sufficiently low GWP above, a refrigeration cycle can be performed.

According to the technique of ninth group using any one of refrigerants having a sufficiently low GWP above, a decrease in capacity can be suppressed.

According to the technique of tenth group using any one of refrigerants having a sufficiently low GWP above, the number of rotations of the motor can be changed in accordance with an air conditioning load, which enables high efficiency of the compressor.

According to the technique of eleventh group using any one of refrigerants having a sufficiently low GWP above, energy efficiency can be good.

According to the technique of twelfth group using any one of refrigerants having a sufficiently low GWP above, high power at comparatively low costs can be achieved by using an induction motor in the compressor.

According to the technique of thirteenth group using any one of refrigerants having a sufficiently low GWP above, the motor rotation rate of the compressor can be changed in accordance with an air conditioning load, and thus a high annual performance factor (APF) can be achieved.

According to the technique of fourteenth group using any one of refrigerants having a sufficiently low GWP above, it is possible to provide the air conditioner that is environmentally friendly.

According to the technique of fifteenth group using any one of refrigerants having a sufficiently low GWP above, warm water can be efficiently generated.

According to the technique of sixteenth group using any one of refrigerants having a sufficiently low GWP above, the material cost of the heat exchanger can be decreased.

According to the technique of seventeenth group using any one of refrigerants having a sufficiently low GWP above, it is possible to reduce the amount of refrigerant with which the air conditioning apparatus is filled.

According to the technique of eighteenth group using any one of refrigerants having a sufficiently low GWP above, the capacity of heat exchange of the heat-source-side heat exchanger can be increased.

According to the technique of nineteenth group using any one of refrigerants having a sufficiently low GWP above, it is possible to cool the control circuit.

According to the technique of twentieth group using any one of refrigerants having a sufficiently low GWP above, the reheat dehumidification operation can be appropriately performed.

According to the technique of twenty-first group using any one of refrigerants having a sufficiently low GWP above, the refrigerant circuit that can perform dehumidification by evaporating the refrigerant in the evaporation zone and that is simplified.

According to the technique of twenty-second group using any one of refrigerants having a sufficiently low GWP above, highly efficient operation can be achieved.

According to the technique of twenty-third group using any one of refrigerants having a sufficiently low GWP above, even if the liquid-side refrigerant connection pipe and the gas-side refrigerant connection pipe are increased in diameter to minimize pressure loss, an increase in cost is minimized by using a pipe made of aluminum or aluminum alloy.

According to the technique of twenty-fourth group using any one of refrigerants having a sufficiently low GWP above, the thermal storage tank can store the resultant cold.

According to the technique of twenty-fifth group using any one of refrigerants having a sufficiently low GWP above, the efficiency of heat exchange can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an apparatus used in a flammability test.

FIG. 2A is a diagram showing points A to M and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass %.

FIG. 2B is a diagram showing points A to C. B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass %.

FIG. 2C is a diagram showing points A to C, B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 95 mass % (R32 content is 5 mass %).

FIG. 2D is a diagram showing points A to C, B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 90 mass % (R32 content is 10 mass %).

FIG. 2E is a diagram showing points A to C, B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 85.7 mass % (R32 content is 14.3 mass %).

FIG. 2F is a diagram showing points A to C. B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 83.5 mass % (R32 content is 16.5 mass %).

FIG. 2G is a diagram showing points A to C, B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 80.8 mass % (R32 content is 19.2 mass %).

FIG. 2H is a diagram showing points A to C, B′ and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 78.2 mass % (R32 content is 21.8 mass %).

FIG. 2I is a diagram showing points A to K and O to R, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass %.

FIG. 2J is a diagram showing points A to D, A′ to D′, and O, and line segments that connect these points to each other in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass %.

FIG. 3A is a schematic configuration diagram of a refrigerant circuit according to a first embodiment of the technique of third group.

FIG. 3B is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the first embodiment of the technique of third group.

FIG. 3C is a schematic configuration diagram of a refrigerant circuit according to a second embodiment of the technique of third group.

FIG. 3D is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the second embodiment of the technique of third group.

FIG. 3E is a schematic configuration diagram of a refrigerant circuit according to a third embodiment of the technique of third group.

FIG. 3F is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the third embodiment of the technique of third group.

FIG. 3G is a schematic configuration diagram of a refrigerant circuit according to a fourth embodiment of the technique of third group.

FIG. 3H is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the fourth embodiment of the technique of third group.

FIG. 3I is a schematic configuration diagram of a refrigerant circuit according to a fifth embodiment of the technique of third group.

FIG. 3J is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the fifth embodiment of the technique of third group.

FIG. 3K is a schematic configuration diagram of a refrigerant circuit according to a sixth embodiment of the technique of third group.

FIG. 3L is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the sixth embodiment of the technique of third group.

FIG. 3M is a schematic configuration diagram of a refrigerant circuit according to a seventh embodiment of the technique of third group.

FIG. 3N is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the seventh embodiment of the technique of third group.

FIG. 3O is a schematic configuration diagram of a refrigerant circuit according to an eighth embodiment of the technique of third group.

FIG. 3P is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the eighth embodiment of the technique of third group.

FIG. 3Q is a schematic configuration diagram of a refrigerant circuit according to a ninth embodiment of the technique of third group.

FIG. 3R is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the ninth embodiment of the technique of third group.

FIG. 3S is a schematic configuration diagram of a refrigerant circuit according to a tenth embodiment of the technique of third group.

FIG. 3T is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the tenth embodiment of the technique of third group.

FIG. 3U is a schematic configuration diagram of a refrigerant circuit according to an eleventh embodiment of the technique of third group.

FIG. 3V is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the eleventh embodiment of the technique of third group.

FIG. 3W is a schematic configuration diagram of a refrigerant circuit according to a twelfth embodiment of the technique of third group.

FIG. 3X is a schematic control block configuration diagram of a refrigeration cycle apparatus according to the twelfth embodiment of the technique of third group.

FIG. 4A is a configuration diagram of an air conditioner according to a first embodiment of the technique of thirteenth group.

FIG. 4B is a circuit block diagram of a power conversion device mounted in an air conditioner according to the first embodiment of the technique of thirteenth group.

FIG. 4C is a circuit block diagram of a power conversion device according to a modification example of the first embodiment of the technique of thirteenth group.

FIG. 4D is a circuit block diagram of a power conversion device mounted in an air conditioner according to a second embodiment of the technique of thirteenth group.

FIG. 4E is a circuit block diagram of a power conversion device according to a modification example of the second embodiment of the technique of thirteenth group.

FIG. 4F is a circuit block diagram of a power conversion device mounted in an air conditioner according to a third embodiment of the technique of thirteenth group.

FIG. 4G is a circuit diagram conceptionally illustrating a bidirectional switch of the technique of thirteenth group.

FIG. 4H is a circuit diagram illustrating an example of a current direction in a matrix converter of the technique of thirteenth group.

FIG. 4I is a circuit diagram illustrating an example of another current direction in the matrix converter of the technique of thirteenth group.

FIG. 4J is a circuit block diagram of a power conversion device according to a modification example of the third embodiment of the technique of thirteenth group.

FIG. 4K is a circuit diagram of a clamp circuit of the technique of thirteenth group.

FIG. 5A is a configuration diagram of an air conditioner according to one embodiment of the technique of fourteenth group.

FIG. 5B is an operation circuit diagram of a motor of a compressor of the technique of fourteenth group.

FIG. 5C is an operation circuit diagram of a motor of a compressor in an air conditioner according to a modification example of the technique of fourteenth group.

FIG. 6A is an external view of a warm-water supply system serving as a warm-water generating apparatus according to a first embodiment of the technique of fifteenth group.

FIG. 6B is a water-circuit and refrigerant-circuit diagram of the warm-water supply system according to the first embodiment of the technique of fifteenth group.

FIG. 6C is a control block diagram of the warm-water supply system according to a first embodiment of the technique of fifteenth group.

FIG. 6D is a water-circuit and refrigerant-circuit diagram of a warm-water supply system according to a first modification of the first embodiment of the technique of fifteenth group.

FIG. 6E is a water-circuit and refrigerant-circuit diagram of a warm-water supply system according to a second modification of the first embodiment of the technique of fifteenth group.

FIG. 6F illustrates a part of a configuration of a warm-water circulation heating system serving as a warm-water generating apparatus according to a second embodiment of the technique of fifteenth group.

FIG. 6G illustrates a part of the configuration of the warm-water circulation heating system according to the second embodiment of the technique of fifteenth group.

FIG. 6H illustrates a part of the configuration of the warm-water circulation heating system according to the second embodiment of the technique of fifteenth group.

FIG. 6I is a control block diagram of the warm-water circulation heating system according to the second embodiment of the technique of fifteenth group.

FIG. 6J illustrates a part of a configuration of a warm-water circulation heating system according to a first modification of the second embodiment of the technique of fifteenth group.

FIG. 6K illustrates a part of a configuration of a warm-water circulation heating system according to a second modification of the second embodiment of the technique of fifteenth group.

FIG. 6L is a schematic configuration diagram of a warm-water supply system serving as a warm-water generating apparatus according to a third embodiment of the technique of fifteenth group.

FIG. 6M is a schematic configuration diagram of a heat source unit of the warm-water supply system according to the third embodiment of the technique of fifteenth group.

FIG. 6N is a control block diagram of the warm-water supply system according to the third embodiment of the technique of fifteenth group.

FIG. 7A is a schematic view showing a disposition of an air conditioning apparatus according to a first embodiment of the technique of seventeenth group.

FIG. 7B is a schematic structural view of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7C is a block diagram showing an electrical connection state of a controller and a thermostat in an air conditioning system according to the first embodiment of the technique of seventeenth group.

FIG. 7D is a perspective view of a state in which an air conditioning apparatus according to a second embodiment of the technique of seventeenth group is installed in a building.

FIG. 7E is a perspective view showing an external appearance of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7F is a perspective view showing the external appearance of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7G is a perspective view for describing an internal structure of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7H is a perspective view for describing the internal structure of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7I is a perspective view for describing the internal structure of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7J is a perspective view for describing ducts of the air conditioning apparatus of the technique of seventeenth group.

FIG. 7K illustrates a refrigerant circuit of the air conditioning apparatus according to the second embodiment of the technique of seventeenth group.

FIG. 7L is a block diagram for describing a control system of the air conditioning apparatus according to the second embodiment of the technique of seventeenth group.

FIG. 7M is a partial enlarged perspective view of the vicinity of a left side portion of a use-side heat exchanger of the technique of seventeenth group.

FIG. 7N is a schematic view for describing positional relationships between a first opening and a second opening and each member of the technique of seventeenth group.

FIG. 7O is a schematic view showing a structure of an air conditioning apparatus according to a third embodiment of the technique of seventeenth group.

FIG. 8A is a schematic view of an example of a counter-flow-type heat exchanger according to an embodiment of the technique of twenty-second group.

FIG. 8B a schematic view of another example of a counter-flow-type heat exchanger according to the embodiment of the technique of twenty-second group; (a) is a plan view and (b) is a perspective view.

FIG. 8C is a schematic structural diagram of a form of a configuration of a refrigerant circuit in a refrigeration cycle apparatus according to a first embodiment of the technique of twenty-second group.

FIG. 8D is a schematic structural diagram of a modification of the refrigerant circuit of FIG. 8C.

FIG. 8E is a schematic structural diagram of a modification of the refrigerant circuit of FIG. 8D.

FIG. 8F is a schematic structural diagram of a modification of the refrigerant circuit of FIG. 8D.

FIG. 8G is a schematic structural diagram of a configuration of a refrigerant circuit of an air conditioning apparatus as an example of a refrigeration cycle apparatus according to a second embodiment of the technique of twenty-second group.

FIG. 8H is a schematic control block structural diagram of the air conditioning apparatus of FIG. 8G.

FIG. 8I is a schematic structural diagram of a configuration of a refrigerant circuit of an air conditioning apparatus as an example of a refrigeration cycle apparatus according to a third embodiment of the technique of twenty-second group.

FIG. 8J is a schematic control block structural diagram of the air conditioning apparatus of FIG. 8I.

FIG. 9A is a schematic configuration diagram of a heat load treatment system that is a refrigeration apparatus according to a first embodiment of the technique of twenty-fifth group.

FIG. 9B is a schematic diagram illustrating an installation layout of the heat load treatment system according to the first embodiment of the technique of twenty-fifth group.

FIG. 9C illustrates a control block of the heat load treatment system according to the first embodiment of the technique of twenty-fifth group.

FIG. 9D is a diagram illustrating refrigerant circuits included in a two-stage refrigeration apparatus that is a refrigeration apparatus according to a second embodiment of the technique of twenty-fifth group.

FIG. 9E is a circuit configuration diagram of an air-conditioning hot water supply system that is a refrigeration apparatus according to the second embodiment of the technique of twenty-fifth group.

DESCRIPTION OF EMBODIMENTS 1 (1-1) Definition of Terms

In the present specification, the term “refrigerant” includes at least compounds that are specified in ISO 817 (International Organization for Standardization), and that are given a refrigerant number (ASHRAE number) representing the type of refrigerant with “R” at the beginning; and further includes refrigerants that have properties equivalent to those of such refrigerants, even though a refrigerant number is not yet given. Refrigerants are broadly divided into fluorocarbon compounds and non-fluorocarbon compounds in terms of the structure of the compounds. Fluorocarbon compounds include chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC), and hydrofluorocarbons (HFC). Non-fluorocarbon compounds include propane (R290), propylene (R1270), butane (R600), isobutane (R600a), carbon dioxide (R744), ammonia (R717), and the like.

In the present specification, the phrase “composition comprising a refrigerant” at least includes (1) a refrigerant itself (including a mixture of refrigerants), (2) a composition that further comprises other components and that can be mixed with at least a refrigeration oil to obtain a working fluid for a refrigerating machine, and (3) a working fluid for a refrigerating machine containing a refrigeration oil. In the present specification, of these three embodiments, the composition (2) is referred to as a “refrigerant composition” so as to distinguish it from a refrigerant itself (including a mixture of refrigerants). Further, the working fluid for a refrigerating machine (3) is referred to as a “refrigeration oil-containing working fluid” so as to distinguish it from the “refrigerant composition.”

In the present specification, when the term “alternative” is used in a context in which the first refrigerant is replaced with the second refrigerant, the first type of “alternative” means that equipment designed for operation using the first refrigerant can be operated using the second refrigerant under optimum conditions, optionally with changes of only a few parts (at least one of the following: refrigeration oil, gasket, packing, expansion valve, dryer, and other parts) and equipment adjustment. In other words, this type of alternative means that the same equipment is operated with an alternative refrigerant. Embodiments of this type of “alternative” include “drop-in alternative,” “nearly drop-in alternative,” and “retrofit,” in the order in which the extent of changes and adjustment necessary for replacing the first refrigerant with the second refrigerant is smaller.

The term “alternative” also includes a second type of “alternative,” which means that equipment designed for operation using the second refrigerant is operated for the same use as the existing use with the first refrigerant by using the second refrigerant. This type of alternative means that the same use is achieved with an alternative refrigerant.

In the present specification, the term “refrigerating machine” refers to machines in general that draw heat from an object or space to make its temperature lower than the temperature of ambient air, and maintain a low temperature. In other words, refrigerating machines refer to conversion machines that gain energy from the outside to do work, and that perform energy conversion, in order to transfer heat from where the temperature is lower to where the temperature is higher.

In the present specification, a refrigerant having a “lower flammability” means that it is determined to be “Class 2L” according to the US ANSI/ASHRAE Standard 34-2013.

(1-2) Refrigerant

Although the details thereof are described later, any one of the refrigerants A, B, C, and D according to the present disclosure (sometimes referred to as “the refrigerant according to the present disclosure”) can be used as a refrigerant.

(1-3) Refrigerant Composition

The refrigerant composition according to the present disclosure comprises at least the refrigerant according to the present disclosure, and can be used for the same use as the refrigerant according to the present disclosure. Moreover, the refrigerant composition according to the present disclosure can be further mixed with at least a refrigeration oil to thereby obtain a working fluid for a refrigerating machine.

The refrigerant composition according to the present disclosure further comprises at least one other component in addition to the refrigerant according to the present disclosure. The refrigerant composition according to the present disclosure may comprise at least one of the following other components, if necessary. As described above, w % ben the refrigerant composition according to the present disclosure is used as a working fluid in a refrigerating machine, it is generally used as a mixture with at least a refrigeration oil. Therefore, it is preferable that the refrigerant composition according to the present disclosure does not substantially comprise a refrigeration oil. Specifically, in the refrigerant composition according to the present disclosure, the content of the refrigeration oil based on the entire refrigerant composition is preferably 0 to 1 mass %, and more preferably 0 to 0.1 mass %.

(1-3-1) Water

The refrigerant composition according to the present disclosure may contain a small amount of water. The water content of the refrigerant composition is preferably 0.1 mass % or less based on the entire refrigerant. A small amount of water contained in the refrigerant composition stabilizes double bonds in the molecules of unsaturated fluorocarbon compounds that can be present in the refrigerant, and makes it less likely that the unsaturated fluorocarbon compounds will be oxidized, thus increasing the stability of the refrigerant composition.

(1-3-2) Tracer

A tracer is added to the refrigerant composition according to the present disclosure at a detectable concentration such that when the refrigerant composition has been diluted, contaminated, or undergone other changes, the tracer can trace the changes.

The refrigerant composition according to the present disclosure may comprise a single tracer, or two or more tracers.

The tracer is not limited, and can be suitably selected from commonly used tracers.

Examples of tracers include hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons, hydrochlorocarbons, fluorocarbons, deuterated hydrocarbons, deuterated hydrofluorocarbons, perfluorocarbons, fluoroethers, brominated compounds, iodinated compounds, alcohols, aldehydes, ketones, and nitrous oxide (N₂O). The tracer is particularly preferably a hydrofluorocarbon, a hydrochlorofluorocarbon, a chlorofluorocarbon, a hydrochlorocarbon, a fluorocarbon, or a fluoroether.

The following compounds are preferable as the tracer.

FC-14 (tetrafluoromethane, CF₄) HCC-40 (chloromethane, CH₃Cl) HFC-23 (trifluoromethane, CHF₃) HFC-41 (fluoromethane, CH₃Cl) HFC-125 (pentafluoroethane, CF₃CHF₂) HFC-134a (1,1,1,2-tetrafluoroethane, CF₃CH₂F) HFC-134 (1,1,2,2-tetrafluoroethane, CHF₂CHF₂) HFC-143a (1,1,1-trifluoroethane, CF₃CH₃) HFC-143 (1,1,2-trifluoroethane, CHF₂CH₂F) HFC-152a (1,1-difluoroethane, CHF₂CH₃) HFC-152 (1,2-difluoroethane, CH₂FCH₂F) HFC-161 (fluoroethane, CH₃CH₂F) HFC-245fa (1,1,1,3,3-pentafluoropropane, CF₃CH₂CHF₂) HFC-236fa (1,1,1,3,3,3-hexafluoropropane, CF₃CH₂CF₃) HFC-236ea (1,1,1,2,3,3-hexafluoropropane, CF₃CHFCHF₂) HFC-227ea (1,1,1,2,3,3,3-heptafluoropropane, CF₃CHFCF₃) HCFC-22 (chlorodifluoromethane, CHClF₂) HCFC-31 (chlorofluoromethane, CH₂ClF) CFC-1113 (chlorotrifluoroethylene, CF₂═CClF) HFE-125 (trifluoromethyl-difluoromethyl ether, CF₃OCHF₂) HFE-134a (trifluoromethyl-fluoromethyl ether, CF₃OCH₂F) HFE-143a (trifluoromethyl-methyl ether, CF₃OCH₃) HFE-227ea (trifluoromethyl-tetrafluoroethyl ether, CF₃OCHFCF₃) HFE-236fa (trifluoromethyl-trifluoroethyl ether, CF₃OCH₂CF₃)

The refrigerant composition according to the present disclosure may contain one or more tracers at a total concentration of about 10 parts per million by weight (ppm) to about 1000 ppm, based on the entire refrigerant composition. The refrigerant composition according to the present disclosure may preferably contain one or more tracers at a total concentration of about 30 ppm to about 500 ppm, and more preferably about 50 ppm to about 300 ppm, based on the entire refrigerant composition.

(1-3-3) Ultraviolet Fluorescent Dye

The refrigerant composition according to the present disclosure may comprise a single ultraviolet fluorescent dye, or two or more ultraviolet fluorescent dyes.

The ultraviolet fluorescent dye is not limited, and can be suitably selected from commonly used ultraviolet fluorescent dyes.

Examples of ultraviolet fluorescent dyes include naphthalimide, coumarin, anthracene, phenanthrene, xanthene, thioxanthene, naphthoxanthene, fluorescein, and derivatives thereof. The ultraviolet fluorescent dye is particularly preferably either naphthalimide or coumarin, or both.

(1-3-4) Stabilizer

The refrigerant composition according to the present disclosure may comprise a single stabilizer, or two or more stabilizers.

The stabilizer is not limited, and can be suitably selected from commonly used stabilizers.

Examples of stabilizers include nitro compounds, ethers, and amines.

Examples of nitro compounds include aliphatic nitro compounds, such as nitromethane and nitroethane; and aromatic nitro compounds, such as nitro benzene and nitro styrene.

Examples of ethers include 1,4-dioxane.

Examples of amines include 2,2,3,3,3-pentafluoropropylamine and diphenylamine.

Examples of stabilizers also include butylhydroxyxylene and benzotriazole.

The content of the stabilizer is not limited. Generally, the content of the stabilizer is preferably 0.01 to 5 mass %, and more preferably 0.05 to 2 mass %, based on the entire refrigerant.

(1-3-5) Polymerization Inhibitor

The refrigerant composition according to the present disclosure may comprise a single polymerization inhibitor, or two or more polymerization inhibitors.

The polymerization inhibitor is not limited, and can be suitably selected from commonly used polymerization inhibitors.

Examples of polymerization inhibitors include 4-methoxy-1-naphthol, hydroquinone, hydroquinone methyl ether, dimethyl-t-butylphenol, 2,6-di-tert-butyl-p-cresol, and benzotriazole.

The content of the polymerization inhibitor is not limited. Generally, the content of the polymerization inhibitor is preferably 0.01 to 5 mass %, and more preferably 0.05 to 2 mass %, based on the entire refrigerant.

(1-4) Refrigeration Oil-Containing Working Fluid

The refrigeration oil-containing working fluid according to the present disclosure comprises at least the refrigerant or refrigerant composition according to the present disclosure and a refrigeration oil, for use as a working fluid in a refrigerating machine. Specifically, the refrigeration oil-containing working fluid according to the present disclosure is obtained by mixing a refrigeration oil used in a compressor of a refrigerating machine with the refrigerant or the refrigerant composition. The refrigeration oil-containing working fluid generally comprises 10 to 50 mass % of refrigeration oil.

(1-4-1) Refrigeration Oil

The composition according to the present disclosure may comprise a single refrigeration oil, or two or more refrigeration oils.

The refrigeration oil is not limited, and can be suitably selected from commonly used refrigeration oils. In this case, refrigeration oils that are superior in the action of increasing the miscibility with the mixture and the stability of the mixture, for example, are suitably selected as necessary.

The base oil of the refrigeration oil is preferably, for example, at least one member selected from the group consisting of polyalkylene glycols (PAG), polyol esters (POE), and polyvinyl ethers (PVE).

The refrigeration oil may further contain additives in addition to the base oil. The additive may be at least one member selected from the group consisting of antioxidants, extreme-pressure agents, acid scavengers, oxygen scavengers, copper deactivators, rust inhibitors, oil agents, and antifoaming agents.

A refrigeration oil with a kinematic viscosity of 5 to 400 cSt at 40° C. is preferable from the standpoint of lubrication.

The refrigeration oil-containing working fluid according to the present disclosure may further optionally contain at least one additive. Examples of additives include compatibilizing agents described below.

(1-4-2) Compatibilizing Agent

The refrigeration oil-containing working fluid according to the present disclosure may comprise a single compatibilizing agent, or two or more compatibilizing agents.

The compatibilizing agent is not limited, and can be suitably selected from commonly used compatibilizing agents.

Examples of compatibilizing agents include polyoxyalkylene glycol ethers, amides, nitriles, ketones, chlorocarbons, esters, lactones, aryl ethers, fluoroethers, and 1,1,1-trifluoroalkanes. The compatibilizing agent is particularly preferably a polyoxyalkylene glycol ether.

(1-5) Various Refrigerants

Refrigerants A to D used in the present disclosure are described below in detail. The disclosures of the refrigerant A, the refrigerant B, the refrigerant C, and the refrigerant D are independent from each other. Thus, the alphabetical letters used for points and line segments, as well as the numbers used for Examples and Comparative Examples, are all independent in each of the refrigerant A, the refrigerant B, the refrigerant C, and the refrigerant D. For example, Example 1 of the refrigerant A and Example 1 of the refrigerant B each represent an example according to a different embodiment.

(1-5-1) Refrigerant A

Refrigerant A according to the present disclosure is a mixed refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and 2,3,3,3-tetrafluoro-1-propene (R1234yf).

The refrigerant A according to the present disclosure has various properties that are desirable as an R410A-alternative refrigerant, i.e., a refrigerating capacity and a coefficient of performance that are equivalent to those of R410A, and a sufficiently low GWP.

The refrigerant A according to the present disclosure is a composition comprising HFO-1132(E) and R1234yf, and optionally further comprising HFO-1123, and may further satisfy the following requirements. This refrigerant A also has various properties desirable as an alternative refrigerant for R410A: i.e., it has a refrigerating capacity and a coefficient of performance that are equivalent to those of R410A, and a sufficiently low GWP.

Requirements

When the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z,

coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments OD, DG, GH, and HO that connect the following 4 points:

point D (87.6, 0.0, 12.4), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DG, and GH (excluding the points O and H);

the line segment DG is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment GH is represented by coordinates (−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and the lines HO and OD are straight lines.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 92.5% or more relative to that of R410A, and a COP ratio of 92.5% or more relative to that of R410A.

The refrigerant A according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments LG, GH, HI, and IL that connect the following 4 points:

point L (72.5, 10.2, 17.3), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point I (72.5, 27.5, 0.0), or on the line segments LG, GH, and IL (excluding the points H and I),

the line segment LG is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment GH is represented by coordinates (−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and

the line segments HI and IL are straight lines.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 92.5% or more relative to that of R410A, and a COP ratio of 92.5% or more relative to that of R410A; furthermore, the refrigerant has a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant A according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments OD, DE, EF, and FO that connect the following 4 points:

point D (87.6, 0.0, 12.4), point E (31.1, 42.9, 26.0), point F (65.5, 34.5, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DE, and EF (excluding the points O and F);

the line segment DE is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment EF is represented by coordinates (−0.0064z²−1.1565z+65.501, 0.0064z²+0.1565z+34.499, z), and

the line segments FO and OD are straight lines.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 93.5% or more relative to that of R410A, and a COP ratio of 93.5% or more relative to that of R410A.

The refrigerant A according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z,

coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments LE, EF, FI, and IL that connect the following 4 points.

point L (72.5, 10.2, 17.3), point E (31.1, 42.9, 26.0), point F (65.5, 34.5, 0.0), and point I (72.5, 27.5, 0.0), or on the line segments LE, EF, and IL (excluding the points F and I);

the line segment LE is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402),

the line segment EF is represented by coordinates (−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and

the line segments FI and IL are straight lines.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 93.5% or more relative to that of R410A, and a COP ratio of 93.5% or more relative to that of R410A; furthermore, the refrigerant has a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant A according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z,

coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within a figure surrounded by line segments OA, AB, BC, and CO that connect the following 4 points:

point A (93.4, 0.0, 6.6), point B (55.6, 26.6, 17.8), point C (77.6, 22.4, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OA, AB, and BC (excluding the points O and C);

the line segment AB is represented by coordinates (0.0052y²−1.5588y+93.385, y, −0.0052y²+0.5588y+6.615),

the line segment BC is represented by coordinates (−0.0032z²−1.1791z+77.593, 0.0032z²+0.1791 z+22.407, z), and

the line segments CO and OA are straight lines.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 95% or more relative to that of R410A, and a COP ratio of 95% or more relative to that of R410A.

The refrigerant A according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z,

coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within a figure surrounded by line segments KB, BJ, and JK that connect the following 3 points:

point K (72.5, 14.1, 13.4), point B (55.6, 26.6, 17.8), and point J (72.5, 23.2, 4.3), or on the line segments KB, BJ, and JK;

the line segment KB is represented by coordinates (0.0052y²−1.5588y+93.385, y, and −0.0052y²+0.5588y+6.615),

the line segment BJ is represented by coordinates (−0.0032z²−1.1791z+77.593, 0.0032z²+0.1791z+22.407, z), and

the line segment JK is a straight line.

When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 95% or more relative to that of R410A, and a COP ratio of 95% or more relative to that of R410A; furthermore, the refrigerant has a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant A according to the present disclosure may further comprise difluoromethane (R32) in addition to HFO-1132(E), HFO-1123, and R1234yf as long as the above properties and effects are not impaired. The content of R32 based on the entire refrigerant A according to the present disclosure is not limited and can be selected from a wide range. For example, when the R32 content of the refrigerant A according to the present disclosure is 21.8 mass %, the mixed refrigerant has a GWP of 150. Therefore, the R32 content can be 21.8 mass % or less. The R32 content of the refrigerant A according to the present disclosure may be, for example, 5 mass % or more, based on the entire refrigerant.

When the refrigerant A according to the present disclosure further contains R32 in addition to HFO-1132(E), HFO-1123, and R1234yf, the refrigerant may be a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum is respectively represented by x, y, z, and a,

if 0<a≤10.0, coordinates (x,y,z) in a ternary composition diagram (FIG. 3 to 9 ) in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.02a²−2.46a+93.4, 0, −0.02a²+2.46a+6.6), point B′ (−0.008a²−1.38a+56, 0.018a²−0.53a+26.3, −0.01a²+1.91a+17.7), point C (−0.016a²+1.02a+77.6, 0.016a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C):

if 10.0<a≤16.5, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0244a²−2.5695a+94.056, 0, −0.0244a²+2.5695a+5.944), point B′ (0.1161a²−1.9959a+59.749, 0.014a²−0.3399a+24.8, −0.1301a²+2.3358a+15.451), point C (−0.0161a²+1.02a+77.6, 0.0161a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C): or

if 16.5<a≤21.8, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0161a²−2.3535a+92.742, 0, −0.0161a²+2.3535a+7.258), point B′ (−0.0435a²−0.0435a+50.406, −0.0304a²+1.8991a−0.0661, 0.0739a²−1.8556a+49.6601), point C (−0.0161a²+0.9959a+77.851, 0.0161a²−0.9959a+22.149, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C). Note that when point B in the ternary composition diagram is defined as a point where a refrigerating capacity ratio of 95% relative to that of R410A and a COP ratio of 95% relative to that of R410A are both achieved, point B′ is the intersection of straight line AB and an approximate line formed by connecting the points where the COP ratio relative to that of R410A is 95%. When the requirements above are satisfied, the refrigerant A according to the present disclosure has a refrigerating capacity ratio of 95% or more relative to that of R410A, and a COP ratio of 95% or more relative to that of R410A.

The refrigerant A according to the present disclosure may further comprise other additional refrigerants in addition to HFO-1132(E), HFO-1123, R1234yf, and R32 as long as the above properties and effects are not impaired. In this respect, the refrigerant A according to the present disclosure preferably comprises HFO-1132(E), HFO-1123, R1234yf, and R32 in a total amount of 99.5 mass % or more, more preferably 99.75 mass % or more, and still more preferably 99.9 mass % or more, based on the entire refrigerant A.

The refrigerant A according to the present disclosure may comprise HFO-1132(E), HFO-1123, and R1234yf in a total amount of 99.5 mass % or more, 99.75 mass % or more, or 99.9 mass % or more, based on the entire refrigerant A.

The refrigerant A according to the present disclosure may comprise HFO-1132(E), HFO-1123, R1234yf, and R32 in a total amount of 99.5 mass % or more, 99.75 mass % or more, or 99.9 mass % or more, based on the entire refrigerant A.

The additional refrigerants are not limited, and can be selected from a wide range of refrigerants. The mixed refrigerant may comprise a single additional refrigerant, or two or more additional refrigerants.

The refrigerant A according to the present disclosure is suitable for use as an alternative refrigerant for R410A.

Examples of Refrigerant A

The refrigerant A is described in more detail below with reference to Examples. However, the refrigerant A according to the present disclosure is not limited to the Examples.

Mixed refrigerants were prepared by mixing HFO-1132(E), HFO-1123, and R1234yf at mass % based on their sum shown in Tables 1 to 5.

The COP ratio and the refrigerating capacity ratio of the mixed refrigerants relative to those of R410 were determined. The conditions for calculation were as described below.

Evaporating temperature: 5° C. Condensation temperature: 45° C. Degree of superheating: 1 K Degree of subcooling: 5 K E_(comp) (compressive modulus): 0.7 kWh

Tables 1 to 5 show these values together with the GWP of each mixed refrigerant.

TABLE 1 Comp. Example 1 Example 6 Item Unit Ex. 1 A Example 2 Example 3 Example 4 Example 5 B HFO- mass % R410A 93.4 85.7 78.3 71.2 64.3 55.6 1132(E) HFO-1123 mass % 0.0 5.0 10.0 15.0 20.0 26.6 R1234yf mass % 6.6 9.3 11.7 13.8 15.7 17.8 GWP — 2088 1 1 1 1 1 2 COP ratio % 100 98.0 97.5 96.9 96.3 95.8 95.0 (relative to R410A) Refrigerating % 100 95.0 95.0 95.0 95.0 95.0 95.0 capacity (relative ratio to R410A)

TABLE 2 Comp. Ex. 2 Example Example Example Item Unit C 7 8 9 HFO-1132(E) mass % 77.6 71.6 65.5 59.2 HFO-1123 mass % 22.4 23.4 24.5 25.8 R1234yf mass % 0.0 5.0 10.0 15.0 GWP — 1 1 1 1 COP ratio % 95.0 95.0 95.0 95.0 (relative to R410A) Refrigerating % 102.5 100.5 98.4 96.3 capacity (relative to ratio R410A)

TABLE 3 Example Example 10 Example Example Example Example Example 16 Item Unit D 11 12 13 14 15 G HFO- mass % 87.6 72.9 59.1 46.3 34.4 23.5 18.2 1132(E) HFO-1123 mass % 0.0 10.0 20.0 30.0 40.0 50.0 55.1 R1234yf mass % 12.4 17.1 20.9 23.7 25.6 26.5 26.7 GWP — 1 2 2 2 2 2 2 COP ratio % 98.2 97.1 95.9 94.8 93.8 92.9 92.5 (relative to R410A) Refrigerating % 92.5 92.5 92.5 92.5 92.5 92.5 92.5 capacity (relative ratio to R410A)

TABLE 4 Comp. Comp. Example Ex. 3 Example Example Ex. 4 Example Example 21 Item Unit H 17 18 F 19 20 E HFO- mass % 56.7 44.5 29.7 65.5 53.3 39.8 31.1 1132(E) HFO-1123 mass % 43.3 45.5 50.3 34.5 36.7 40.2 42.9 R1234yf mass % 0.0 10.0 20.0 0.0 10.0 20.0 26.0 GWP — 1 1 2 1 1 2 2 COP ratio % 92.5 92.5 92.5 93.5 93.5 93.5 93.5 (relative to R410A) Refrigerating % 105.8 101.2 96.2 104.5 100.2 95.5 92.5 capacity (relative ratio to R410A)

TABLE 5 Comp. Example Example Example Comp. Ex. 5 22 23 24 Ex. 6 Item Unit I J K L M HFO- mass % 72.5 72.5 72.5 72.5 72.5 1132(E) HFO-1123 mass % 27.5 23.2 14.1 10.2 0.0 R1234yf mass % 0.0 4.3 13.4 17.3 27.5 GWP — 1 1 1 2 2 COP ratio % 94.4 95.0 96.4 97.1 98.8 (relative to R410A) Refrigerating % 103.5. 100.8 95.0 92.5 85.7 capacity (relative ratio to R410A)

These results indicate that under the condition that the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum is respectively represented by x, y, and z, when coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure (FIG. 2 ) surrounded by line segments OD, DG, GH, and HO that connect the following 4 points:

point D (87.6, 0.0, 12.4), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DG, and GH (excluding the points O and H), the refrigerant has a refrigerating capacity ratio of 92.5% or more relative to that of R410A, and a COP ratio of 92.5% or more relative to that of R410A.

Likewise, the results indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 2 ) surrounded by line segments OD, DE, EF, and FO that connect the following 4 points:

point D (87.6, 0.0, 12.4), point E (31.1, 42.9, 26.0), point F (65.5, 34.5, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DE, and EF (excluding the points O and F), the refrigerant has a refrigerating capacity ratio of 93.5% or more relative to that of R410A, and a COP ratio of 93.5% or more relative to that of R410A.

Likewise, the results indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 2 ) surrounded by line segments OA, AB, BC, and CO that connect the following 4 points:

point A (93.4, 0.0, 6.6), point B (55.6, 26.6, 17.8), point C (77.6, 22.4, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OA, AB, and BC (excluding the points O and C), the refrigerant has a refrigerating capacity ratio of 95% or more relative to that of R410A, and a COP ratio of 95% or more relative to that of R410A.

R1234yf contributes to reduction of flammability and reduction of deterioration of polymerization etc. in these compositions. Therefore, the composition according to the present disclosure preferably contains R1234yf.

Further, the burning velocity of these mixed refrigerants was measured according to the ANSI/ASHRAE Standard 34-2013. Compositions that showed a burning velocity of 10 cm/s or less were determined to be Class 2L (lower flammability). These results clearly indicate that when the content of HFO-1132(E) in a mixed refrigerant of HFO-1132(E), HFO-1123, and R1234yf is 72.5 mass % or less based on their sum, the refrigerant can be determined to be Class 2L (lower flammability).

A burning velocity test was performed using the apparatus shown in FIG. 1 in the following manner. First, the mixed refrigerants used had a purity of 99.5% or more, and were degassed by repeating a cycle of freezing, pumping, and thawing until no traces of air were observed on the vacuum gauge. The burning velocity was measured by the closed method. The initial temperature was ambient temperature. Ignition was performed by generating an electric spark between the electrodes in the center of a sample cell. The duration of the discharge was 1.0 to 9.9 ms, and the ignition energy was typically about 0.1 to 1.0 J. The spread of the flame was visualized using schlieren photographs. A cylindrical container (inner diameter: 155 mm, length: 198 mm) equipped with two light transmission acrylic windows was used as the sample cell, and a xenon lamp was used as the light source. Schlieren images of the flame were recorded by a high-speed digital video camera at a frame rate of 600 fps and stored on a PC.

Mixed refrigerants were prepared by mixing HFO-1132(E), HFO-1123, R1234yf, and R32 in amounts shown in Tables 6 to 12, in terms of mass %, based on their sum.

The COP ratio and the refrigerating capacity ratio of these mixed refrigerants relative to those of R410A were determined. The calculation conditions were the same as described above. Tables 6 to 12 show these values together with the GWP of each mixed refrigerant.

TABLE 6 Comp. Comp. Comp. Example Comp. Comp. Comp. Ex. 7 Ex. Ex. 25 Ex. 10 Ex. 11 Item Unit Ex. 1 A 8 9 B′ B Example 26 Example 27 C HFO- mass R410 93.4 78.3 64.3 56.0 55.6 60.0 70.0 77.6 1132(E) % A HFO- mass 0.0 10.0 20.0 26.3 26.6 25.6 23.7 22.4 1123 % R1234yf mass 6.6 11.7 15.7 17.7 17.8 14.4 6.3 0.0 % R32 mass 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 % GWP — 2088 1 1.4 1.5 1.5 1.5 1.4 1.2 1.0 COP ratio % 100 98.0 96.9 95.8 95.0 95.0 95.0 95.0 95.0 (relative to R410 A) Refrigerating % 100 95.0 95.0 95.0 95.0 95.0 96.5 100.0 102.5 capacity (relative ratio to R410 A)

TABLE 7 Comp. Comp. Comp. Example Comp. Comp. Ex. 12 Ex. Ex. 28 Ex. 15 Ex. 16 Item Unit A 13 14 B′ B Example 29 Example 30 C HFO- mass % 81.6 67.3 53.9 48.9 47.2 60.0 70.0 77.3 1132(E) HFO- mass % 0.0 10.0 20.0 24.1 25.3 21.6 19.2 17.7 1123 R1234yf mass % 13.4 17.7 21.1 22.0 22.5 13.4 5.8 0.0 R32 mass % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 GWP — 35 35 35 35 35 35 35 35 COP % 97.6 96.6 95.5 95.0 95.0 95.0 95.0 95.0 ratio (relative to R410A) Refrigerating % 95.0 95.0 95.0 104.4 95.0 99.0 102.1 104.4 capacity (relative ratio to R410A)

TABLE 8 Comp. Comp. Ex. Comp. Comp. Example Ex. Comp. 17 Ex. Ex. 31 20 Example Example Ex. 21 Item Unit A 18 19 B′ B 32 33 C HFO- mass % 70.8 57.2 44.5 41.4 36.4 60.0 70.0 76.2 1132(E) HFO- mass % 0.0 10.0 20.0 22.8 26.7 18.0 15.3 13.8 1123 R1234yf mass % 19.2 22.8 25.5 25.8 26.9 12.0 4.7 0.0 R32 mass % 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 GWP — 69 69 69 69 69 69 69 68 COP % 97.4 96.5 95.6 95.0 95.0 95.0 95.0 95.0 ratio (relative to R410A) Refrigerating % 95.0 95.0 95.0 106.2 95.0 101.5 104.4 106.2 capacity (relative ratio to R410A)

TABLE 9 Comp. Comp. Ex. Comp. Comp. Example Ex. Comp. 22 Ex. Ex. 34 25 Example Example Ex. 26 Item Unit A 23 24 B′ B 35 36 C HFO- mass % 62.3 49.3 37.1 34.5 24.9 60.0 70.0 74.5 1132(E) HFO- mass % 0.0 10.0 20.0 22.8 30.7 15.4 12.4 11.2 1123 R1234yf mass % 23.4 26.4 28.6 28.4 30.1 10.3 3.3 0.0 R32 mass % 14.3 14.3 14.3 14.3 14.3 14.3 14.3 14.3 GWP — 98 98 98 98 98 98 97 97 COP % 97.3 96.5 95.7 95.5 95.0 95.0 95.0 95.0 ratio (relative to R410A) Refrigerating % 95.0 95.0 95.0 95.4 95.0 103.7 106.5 107.7 capacity (relative ratio to R410A)

TABLE 10 Comp. Ex. Comp. Comp. Example Comp. Comp. 27 Ex. Ex. 37 Ex. 30 Example Example Ex. 31 Item Unit A 28 29 B′ B 38 39 C HFO- mass % 58.3 45.5 33.5 31.2 16.5 60.0 70.0 73.4 1132(E) HFO- mass % 0.0 10.0 20.0 23.0 35.5 14.2 11.1 10.1 1123 R1234yf mass % 25.2 28.0 30.0 29.3 31.5 9.3 2.4 0.0 R32 mass % 16.5 16.5 16.5 16.5 16.5 16.5 16.5 16.5 GWP — 113.0 113.1 113.1 113.1 113.2 112.5 112.3 112.2 COP % 97.4 96.6 95.9 95.6 95.0 95.0 95.0 95.0 ratio (relative to R410A) Refrigerating % 95.0 95.0 95.0 95.7 95.0 104.9 107.6 108.5 capacity (relative ratio to R410A)

TABLE 11 Comp. Ex. Comp. Comp. Exam- Comp. Comp. 32 Ex. Ex. ple 40 Ex. 35 Exam- Exam- Ex. 36 Item Unit A 33 34 B B ple 41 ple 42 C HFO- mass % 53.5 41.0 29.3 25.8 0.0 50.0 60.0 71.7 1132(E) HFO- mass % 0.0 10.0 20.0 25.2 48.8 16.8 12.9 9.1 1123 R1234yf mass % 27.3 29.8 31.5 29.8 32.0 14.0 79 0.0 R32 mass % 19.2 19.2 19.2 19.2 19.2 19.2 19.2 19.2 GWP — 131. 131.3 131.4 131.3 131.4 130.8 130.6 130.4 COP % 97.4 96.7 96.1 97.8 95.0 95.0 95.0 95.0 ratio (relative to R410A) Refriger- % 95.0 95.0 95.0 96.3 95.0 104.0 106.4 109.4 ating (relative capacity to ratio R410A)

TABLE 12 Comp. Comp. Ex. Comp. Comp. Exam- Ex. Comp. 37 Ex. Ex. ple 43 40 Exam- Exam- Ex. 41 Item Unit A 38 39 B’ B ple 44 ple 45 C HFO- mass % 49.1 36.9 25.5 20.0 0.0 50.0 60.0 69.7 1132(E) HFO- mass % 0.0 10.0 20.0 26.9 45.3 15.8 11.9 8.5 1123 R1234yf mass % 29.1 31.3 20.0 31.3 32.9 12.4 6.3 0.0 R32 mass % 21.8 21.8 21.8 21.8 21.8 21.8 21.8 21.8 GWP — 148.8 148.9 148.9 148.9 148.9 148.3 148.1 147.9 COP % 97.6 96.9 96.4 95.9 95.5 95.0 95.0 95.0 ratio (relative to R410A) Refriger- % 95.0 95.0 95.0 98.4 95.0 105.6 108.0 110.3 ating (relative capacity to ratio R410A)

These results indicate that the refrigerants according to the present disclosure that satisfy the following conditions have a refrigerating capacity ratio of 95% or more relative to that of R410A, and a COP ratio of 95% or more relative to that of R410A:

when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum is respectively represented by x, y, z, and a,

if 0<a≤10.0, coordinates (x,y,z) in a ternary composition diagram (FIGS. 3 to 9 ) in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.02a²−2.46a+93.4, 0, −0.02a²+2.46a+6.6), point B′ (−0.008a²−1.38a+56, 0.018a²−0.53a+26.3, −0.01a²+1.91a+17.7), point C (−0.016a²+1.02a+77.6, 0.016a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C);

if 10.0<a≤16.5, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0244a²−2.5695a+94.056, 0, −0.0244a²+2.5695a+5.944), point B′ (0.1161a²−1.9959a+59.749, 0.014a²−0.3399a+24.8, −0.1301a²+2.3358a+15.451), point C (−0.0161a²+1.02a+77.6, 0.0161a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C); or

if 16.5<a≤21.8, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points:

point A (0.0161a²−2.3535a+92.742, 0, −0.0161a²+2.3535a+7.258), point B′ (−0.0435a²−0.0435a+50.406, −0.0304a²+1.8991a−0.0661, 0.0739a²−1.8556a+49.6601), point C (−0.0161a²+0.9959a+77.851, 0.0161a²−0.9959a+22.149, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding the points O and C).

FIGS. 3 to 9 show compositions whose R32 content a (mass %) is 0 mass %, 5 mass %. 10 mass %. 14.3 mass %, 16.5 mass %, 19.2 mass %, and 21.8 mass %, respectively.

Note that when point B in the ternary composition diagram is defined as a point where a refrigerating capacity ratio of 95% relative to that of R410A and a COP ratio of 95% relative to that of R410A are both achieved, point B′ is the intersection of straight line AB and an approximate line formed by connecting three points, including point C, where the COP ratio relative to that of R410A is 95%.

Points A, B′, and C were individually obtained by approximate calculation in the following manner.

Point A is a point where the HFO-1123 content is 0 mass % and a refrigerating capacity ratio of 95% relative to that of R410A is achieved. Three points corresponding to point A were obtained in each of the following three ranges by calculation, and their approximate expressions were obtained.

TABLE 13 Item 10.0 ≥ R32 ≥ 0 16.5 ≥ R32 ≥ 10.0 21.8 ≥ R32 ≥ 16.5 R32 0.0 5.0 10.0 10.0 14.3 16.5 16.5 19.2 21.8 HFO- 93.4 81.6 70.8 70.8 62.3 58.3 58.3 53.5 49.1 1132(E) HFO-1123 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 R1234yf 6.6 13.4 19.2 19.2 23.4 25.2 25.2. 27.3 29.1 R32 x x x HFO- 0.02 × 2 − 2.46x + 93.4 0.0244 × 2 − 0.0161 × 2 − 1132(E) 2.5695x + 94.056 2.3535x + 92.742 approximate expression HFO-1123 0 0 0 approximate expression R1234yf 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) approximate expression

Point C is a point where the R1234yf content is 0 mass % and a COP ratio of 95% relative to that of R410A is achieved. Three points corresponding to point C were obtained in each of the following three ranges by calculation, and their approximate expressions were obtained.

TABLE 14 Item 10.0 ≥ R32 ≥ 0 16.5 ≥ R32 ≥ 10.0 21.8 ≥ R32 ≥ 16.5 R32 0 5 10 10 14.3 16.5 16.5 19.2 21.8 HFO-1132(E) 77.6 77.3 76.2 76.2 74.5 73.4 73.4 71.7 69.7 HFO-1123 22.4 17.7 13.8 13.8 11.2 10.1 10.1 9.1 8.5 R1234yf 0 0 0 0 0 0 0 0 0 R32 x x x HFO-1132(E) 100-R32HFO-1123 100-R32HFO-1123 100-R32HFO-1123 approximate expression HFO-1123 0.016 × 2 − 1.02x + 22.4 0.0161 × 2 − 0.0161*2 − approximate 0.9959x + 22.149 0.9959* + 22.149 expression R1234yf 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) approximate expression

Three points corresponding to point B′ were obtained in each of the following three ranges by calculation, and their approximate expressions were obtained.

TABLE 15 Item 10.0 ≥ R32 ≥ 0 16.5 ≥ R32 ≥ 10.0 21.8 ≥ R32 ≥ 16.5 R32 0 5 10 10 14.3 16.5 16.5 19.2 21.8 HFO- 56 48.9 41.4 41.4 34.5 31.2 31.2 25.8 20 1132(E) HFO-1123 26.3 24.1 22 8 20 8 22.8 23 23 25.2 26.9 R1234yf 17.7 22 25.8 25.8 28.4 29.3 29.3 29.8 31.3 R32 x x x HFO- −0.008*2 − 1.38*56 0.0161 × 2 − 1.995 9x + 59.749 −0.0435 × 2 − 1132(E) 0.4456x + 50.406 approximate expression HFO-1123 0.018 × 2 − 0.53x + 263 0.014 × 2 − 0.3399x + 24.8 −0.0304*2 + 1.8991* − approximate 0.0661 expression R1234yf 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) 100-R32-HFO-1132(E) approximate expression

(1-5-2) Refrigerant B

Refrigerant B according to the present disclosure is a mixed refrigerant comprising HFO-1132(E) and HFO-1123 in a total amount of 99.5 mass % or more based on the entire refrigerant B, and the refrigerant B comprising 62.5 mass % to 72.5 mass % of HFO-1132(E) based on the entire refrigerant B.

The refrigerant B according to the present disclosure has various properties that are desirable as an R410A-alternative refrigerant, i.e., (1) a coefficient of performance equivalent to that of R410A. (2) a refrigerating capacity equivalent to that of R410A. (3) a sufficiently low GWP, and (4) a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant B according to the present disclosure is particularly preferably a mixed refrigerant comprising 72.5 mass % or less of HFO-1132(E), because it has a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant B according to the present disclosure is more preferably a mixed refrigerant comprising 62.5 mass % or more of HFO-1132(E). In this case, the refrigerant B according to the present disclosure has a superior coefficient of performance relative to that of R410A, the polymerization reaction of HFO-1132(E) and/or HFO-1123 is further suppressed, and the stability is further improved.

The refrigerant B according to the present disclosure may further comprise other additional refrigerants in addition to HFO-1132(E) and HFO-1123, as long as the above properties and effects are not impaired. In this respect, the refrigerant B according to the present disclosure preferably comprises HFO-1132(E) and HFO-1123 in a total amount of 99.75 mass % or more, and more preferably 99.9 mass % or more, based on the entire refrigerant B.

Such additional refrigerants are not limited, and can be selected from a wide range of refrigerants. The mixed refrigerant may comprise a single additional refrigerant, or two or more additional refrigerants.

The refrigerant B according to the present disclosure is suitable for use as an alternative refrigerant for HFC refrigerants, such as R410A, R407C, and R404A, as well as for HCFC refrigerants, such as R22.

Examples of Refrigerant B

The refrigerant B is described in more detail below with reference to Examples. However, the refrigerant B according to the present disclosure is not limited to the Examples.

Mixed refrigerants were prepared by mixing HFO-1132(E) and HFO-1123 at mass % based on their sum shown in Tables 16 and 17.

The GWP of compositions each comprising a mixture of R410A (R32=50%/R125=50%) was evaluated based on the values stated in the Intergovernmental Panel on Climate Change (IPCC), fourth report. The GWP of HFO-1132(E), which was not stated therein, was assumed to be 1 from HFO-1132a (GWP=1 or less) and HFO-1123 (GWP=0.3, described in PTL 1). The refrigerating capacity of compositions each comprising R410A and a mixture of HFO-1132(E) and HFO-1123 was determined by performing theoretical refrigeration cycle calculations for the mixed refrigerants using the National Institute of Science and Technology (NIST) and Reference Fluid Thermodynamic and Transport Properties Database (Refprop 9.0) under the following conditions.

Evaporating temperature: 5° C. Condensation temperature: 45° C. Superheating temperature: 1 K Subcooling temperature; 5 K Compressor efficiency: 70%

Tables 1 and 2 show GWP, COP, and refrigerating capacity, which were calculated based on these results. The COP and refrigerating capacity are ratios relative to R410A.

The coefficient of performance (COP) was determined by the following formula.

COP=(refrigerating capacity or heating capacity)/power consumption

For the flammability, the burning velocity was measured according to the ANSI/ASHRAE Standard 34-2013. Compositions having a burning velocity of 10 cm/s or less were determined to be “Class 2L (lower flammability).”

A burning velocity test was performed using the apparatus shown in FIG. 1 in the following manner. First, the mixed refrigerants used had a purity of 99.5% or more, and were degassed by repeating a cycle of freezing, pumping, and thawing until no traces of air were observed on the vacuum gauge. The burning velocity was measured by the closed method. The initial temperature was ambient temperature. Ignition was performed by generating an electric spark between the electrodes in the center of a sample cell. The duration of the discharge was 1.0 to 9.9 ins, and the ignition energy was typically about 0.1 to 1.0 J. The spread of the flame was individualized using schlieren photographs. A cylindrical container (inner diameter: 155 mm, length: 198 mm) equipped with two light transmission acrylic windows was used as the sample cell, and a xenon lamp was used as the light source. Schlieren images of the flame were recorded by a high-speed digital video camera at a frame rate of 600 fps and stored on a PC.

TABLE 16 Comp. Comp. Ex. 2 Ex. 1 HFO- Comp. Exam- Exam- Exam- Item Unit R410A H32L Ex. 3 ple 1 ple 2 ple 3 HFO- mass % 0 100 80 72.5 70 67.5 1132E HFO- mass % 0 0 20 27.5 30 32.5 1123 GWP — 2088 1 1 1 1 1 COP ratio % 100 98 95.3 94.4 94.1 93.8 (relative to R410A) Refriger- % 100 98 102.1 103.5 103.9 104.3 ating (relative capacity to ratio R410A) Discharge MPa 2.7 2.7 2.9 3.0 3.0 3.1 pressure Burning cm/sec Non- 20 13 10 9 9 or velocity flammable less

TABLE 17 Comp. Ex. 7 Example Example Comp. Comp. Comp. HFO- Item Unit 4 5 Ex. 4 Ex. 5 Ex. 6 1123 HFO- mass % 65 62.5 60 50 25 0 1132E HFO- mass % 35 37.5 40 50 75 100 1123 GWP — 1 1 1 1 1 1 COP ratio % 93.5 93.2 92.9 91.8 89.9 89.9 (relative to R410A) Refriger- % 104.7 105.0 105.4 106.6 108.1 107.0 ating (relative capacity to ratio R410A) Discharge MPa 3.1 3.1 3.1 3 2 3.4 3.4 pressure Burning cm/sec 9 or less 9 or less 9 or less 9 or less 9 or less 5 velocity

The compositions each comprising 62.5 mass % to 72.5 mass % of HFO-1132(E) based on the entire composition are stable while having a low GWP (GWP=1), and they ensure ASHRAE 2L flammability. Further, surprisingly, they can ensure performance equivalent to that of R410A.

(1-5-3) Refrigerant C

Refrigerant C according to the present disclosure is a mixed refrigerant comprising HFO-1132(E), R32, and 2,3,3,3-tetrafluoro-1-propene (R1234yf).

The refrigerant C according to the present disclosure has various properties that are desirable as an R410A-alternative refrigerant; i.e., a refrigerating capacity equivalent to that of R410A, a sufficiently low GWP, and a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant C according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AC, CF, FD, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point C (36.5, 18.2, 45.3), point F (47.6, 18.3, 34.1), and point D (72.0, 0.0, 28.0), or on these line segments;

the line segment AC is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+28.904),

the line segment FD is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and

the line segments CF and DA are straight lines. When the requirements above are satisfied, the refrigerant C according to the present disclosure has a refrigerating capacity ratio of 85% or more relative to that of R410A, a GWP of 125 or less, and a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant C according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AB, BE, ED, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point B (42.6, 14.5, 42.9), point E (51.4, 14.6, 34.0), and point D (72.0, 0.0, 28.0), or on these line segments:

the line segment AB is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+28.904),

the line segment ED is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and

the line segments BE and DA are straight lines. When the requirements above are satisfied, the refrigerant C according to the present disclosure has a refrigerating capacity ratio of 85% or more relative to that of R410A, a GWP of 100 or less, and a lower flammability (Class 2L) according to the ASHRAE standard.

The refrigerant C according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 1(0) mass % are within the range of a figure surrounded by line segments GI, IJ, and JG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point I (55.1, 18.3, 26.6), and point J (77.5, 18.4, 4.1). or on these line segments;

the line segment GI is represented by coordinates (0.02y²−2.4583y+93.396, y, −0.02y²+1.4583y+6.604), and

the line segments IJ and JG are straight lines. When the requirements above are satisfied, the refrigerant C according to the present disclosure has a refrigerating capacity ratio of 95% or more relative to that of R410A and a GWP of 100 or less, undergoes fewer or no changes such as polymerization or decomposition, and also has excellent stability.

The refrigerant C according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GH, HK, and KG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point H (61.8, 14.6, 23.6), and point K (77.5, 14.6, 7.9), or on these line segments;

the line segment GH is represented by coordinates (0.02y²−2.4583y+93.3%, y, −0.02y²+1.4583y+6.604), and

the line segments HK and KG are straight lines. When the requirements above are satisfied, the refrigerant C according to the present disclosure has a refrigerating capacity ratio of 95% or more relative to that of R410A and a GWP of 100 or less, undergoes fewer or no changes such as polymerization or decomposition, and also has excellent stability.

The refrigerant C according to the present disclosure may further comprise other additional refrigerants in addition to HFO-1132(E), R32, and R1234yf, as long as the above properties and effects are not impaired. In this respect, the refrigerant C according to the present disclosure preferably comprises HFO-1132(E), R32, and R1234yf in a total amount of 99.5 mass % or more, more preferably 99.75 mass % or more, and still more preferably 99.9 mass % or more based on the entire refrigerant C.

Such additional refrigerants are not limited, and can be selected from a wide range of refrigerants. The mixed refrigerant may comprise a single additional refrigerant, or two or more additional refrigerants.

The refrigerant C according to the present disclosure is suitable for use as an alternative refrigerant for R410A.

Examples of Refrigerant C

The refrigerant C is described in more detail below with reference to Examples. However, the refrigerant C according to the present disclosure is not limited to the Examples.

The burning velocity of individual mixed refrigerants of HFO-1132(E), R32, and R1234yf was measured in accordance with the ANSI/ASHRAE Standard 34-2013. A formulation that shows a burning velocity of 10 cm/s was found by changing the concentration of R32 by 5 mass %. Table 18 shows the formulations found.

A burning velocity test was performed using the apparatus shown in FIG. 1 in the following manner. First, the mixed refrigerants used had a purity of 99.5% or more, and were degassed by repeating a cycle of freezing, pumping, and thawing until no traces of air were observed on the vacuum gauge. The burning velocity was measured by the closed method. The initial temperature was ambient temperature. Ignition was performed by generating an electric spark between the electrodes in the center of a sample cell. The duration of the discharge was 1.0 to 9.9 ms, and the ignition energy was typically about 0.1 to 1.0 J. The spread of the flame was visualized using schlieren photographs. A cylindrical container (inner diameter: 155 mm, length. 198 mm) equipped with two light transmission acrylic windows was used as the sample cell, and a xenon lamp was used as the light source. Schlieren images of the flame were recorded by a high-speed digital video camera at a frame rate of 600 fps and stored on a PC.

TABLE 18 R32 = 5 R32 = 10 R32 = 15 R32 = 20 Item Unit Point D mass % mass % mass % mass % HFO- Mass % 72 64 57 51 46 1132E R32 Mass % 0 5 10 15 20 R1234yf Mass % 28 31 33 34 34 Burning cm/s 10 10 10 10 10 Velocity

The results indicate that under the condition that the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, when coordinates (x,y,z) in the ternary composition diagram shown in FIG. 10 in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are on the line segments that connect the 5 points shown in Table 18 or on the right side of the line segments, the refrigerant has a lower flammability (Class 2L) according to the ASHRAE standard.

This is because R1234yf is known to have a lower burning velocity than HFO-1132(E) and R32.

Mixed refrigerants were prepared by mixing HFO-1132(E), R32, and R1234yf in amounts (mass %) shown in Tables 19 to 23 based on the sum of HFO-1132(E), R32, and R1234yf. The coefficient of performance (COP) ratio and the refrigerating capacity ratio relative to those of R410A of the mixed refrigerants shown in Tables 19 to 23 were determined. The conditions for calculation were as described below.

Evaporating temperature: 5° C. Condensation temperature: 45° C. Degree of superheating: 1 K Degree of subcooling: 5 K E_(comp) (compressive modulus): 0.7 kWh

Tables 19 to 23 show these values together with the GWP of each mixed refrigerant.

TABLE 19 Comp. Comp. Ex. 2 Example 3 Example 4 Item Unit Ex. 1 A Example 1 Example 2 B C HFO-1132E Mass % R410A 71.1 60.4 50.6 42.6 36.5 R32 Mass % 0.0 5.0 10.0 14.5 18.2 R1234yf Mass % 28.9 34.6 39.4 42.9 45.3 GWP — 2088 2 36 70 100 125 COP % 100 98.9 98.7 98.7 98.9 99.1 Ratio (relative to R410A) Refrigerating % 100 85.0 85.0 85.0 85.0 85.0 Capacity (relative Ratio to R410A)

TABLE 20 Comp. Comp. Comp. Comp. Ex. 3 Ex. 4 Ex. 5 Ex. 6 Item Unit O P Q R HFO-1132E Mass % 85.3 0.0 81.6 0.0 R32 Mass % 14.7 14.3 18.4 18.1 R1234yf Mass % 0 85.7 0.0 81.9 GWP — 100 100 125 125 COP Ratio % 96.2 103.4 95.9 103.4 (relative to R410A) Refrigerating % 105.7 57.3 107.4 60.9 Capacity (relative to Ratio R410A)

TABLE 21 Comp. Ex. Exam- Exam- Comp. 7 Exam- Exam- ple 7 Exam- ple 9 Ex. Item Unit D ple 5 ple 6 E ple 8 F 8 HFO- Mass % 72.0 64.0 57.0 51.4 51.0 47.6 46.0 1132E R32 Mass % 0.0 5.0 10.0 14.6 15.0 18.3 20.0 R1234yf Mass % 28.0 31.0 33.0 34.0 34.0 34.1 34.0 GWP — 1.84 36 69 100 103 125 137 COP Ratio % 98.8 98.5 98.2 98.1 98.1 98.0 98.0 (relative to R410A) Refrigerating % 85.4 86.8 88.3 89.8 90.0 91.2 91.8 Capacity (relative Ratio to R410A)

TABLE 22 Example Example Comp. Comp. Example 11 12 Item Unit Ex. 9 Ex. 10 10 H I HFO-1132E Mass % 93.4 81.6 70.8 61.8 55.1 R32 Mass % 0.0 5.0 10.0 14.6 18.3 R1234yf Mass % 6.6 13.4 19.2 23.6 26.6 GWP — 1 35 69 100 125 COP Ratio % 98.0 97.6 97.4 97.3 97.4 (relative to R410A) Refrigerating % 95.0 95.0 95.0 95.0 95.0 Capacity (relative Ratio to R410A)

TABLE 23 Example Example Example Comp. 13 14 15 Comp. Item Unit Ex. 11 J K G Ex. 12 HFO-1132E Mass % 77.5 77.5 77.5 77.5 77.5 R32 Mass % 22.5 18.4 14.6 6.9 0.0 R1234yf Mass % 0.0 4.1 7.9 15.6 22.5 GWP — 153 125 100 48.0 2 COP Ratio % 95.8 96.1 96.5 97.5 98.6 (relative to R410A) Refrigerating % 109.1 105.6 102.3 95.0 88.0 Capacity (relative Ratio to R410A)

The results indicate that under the condition that the mass % of HFO-1132(E), R32, and R1234yf based on their sum is respectively represented by x, y, and z, when coordinates (x,y,z) in the ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure (FIG. 10 ) surrounded by line segments AC, CF, FD, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point C (36.5, 18.2, 45.3). point F (47.6, 18.3, 34.1), and point D (72.0, 0.0, 28.0), or on these line segments. the refrigerant has a refrigerating capacity ratio of 85% or more relative to that of R410A, a GWP of 125 or less, and a lower flammability (Class 2L) according to the ASHRAE standard.

Likewise, the results indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 10 ) surrounded by line segments AB, BE, ED, and DA that connect the following 4 points:

point A (71.1, 0.0, 28.9), point B (42.6, 14.5, 42.9), point E (51.4, 14.6, 34.0), and point D (72.0, 0.0, 28.0), or on these line segments, the refrigerant has a refrigerating capacity ratio of 85% or more relative to that of R410A, a GWP of 100 or less, and a lower flammability (Class 2L) according to the ASHRAE standard.

Likewise, the results indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 10 ) surrounded by line segments GI. IJ, and JG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point I (55.1, 18.3, 26.6), and point J (77.5, 18.4, 4.1), or on these line segments, the refrigerant has a refrigerating capacity ratio of 95% or more relative to that of R410A and a GWP of 125 or less, undergoes fewer or no changes such as polymerization or decomposition, and also has excellent stability.

Likewise, the results indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 10 ) surrounded by line segments GH, HK, and KG that connect the following 3 points:

point G (77.5, 6.9, 15.6), point H (61.8, 14.6, 23.6), and point K (77.5, 14.6, 7.9), or on these line segments, the refrigerant has a refrigerating capacity ratio of 95% or more relative to that of R410A and a GWP of 100 or less, undergoes fewer or no changes such as polymerization or decomposition, and also has excellent stability.

(5-4) Refrigerant D

Refrigerant D according to the present disclosure is a mixed refrigerant comprising HFO-1132(E), HFO-1123, and R32.

The refrigerant D according to the present disclosure has various properties that are desirable as an R410A-alternative refrigerant, i.e., a coefficient of performance equivalent to that of R410A and a sufficiently low GWP.

The refrigerant D according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′E′, E′A′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), point E′ (41.8, 39.8, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments C′D′, D′E′, and E′A′ (excluding the points C′ and A′);

the line segment C′D′ is represented by coordinates

(−0.0297z²−0.1915z+56.7, 0.0297z²−1.1915z+43.3, z),

the line segment D′E′ is represented by coordinates

(−0.0535z²+0.3229z+53.957, 0.05352−0.6771z+46.043, z), and

the line segments OC′, E′A′, and A′O are straight lines. When the requirements above are satisfied, the refrigerant D according to the present disclosure has a COP ratio of 92.5% or more relative to that of R410A, and a GWP of 125 or less.

The refrigerant D according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC, CD, DE, EA′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), point E (72.2, 9.4, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments CD, DE, and EA′ (excluding the points C and A′);

the line segment CDE is represented by coordinates

(−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and

the line segments OC, EA′, and A′O are straight lines. When the requirements above are satisfied, the refrigerant D according to the present disclosure has a COP ratio of 95% or more relative to that of R410A, and a GWP of 125 or less.

The refrigerant D according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′A, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments C′D′ and D′A (excluding the points C′ and A);

-   -   the line segment C′D′ is represented by coordinates         (−0.0297z²−0.1915z+56.7, 0.0297z²+1.1915z+43.3, z), and

the line segments OC′, D′A, and AO are straight lines. When the requirements above are satisfied, the refrigerant D according to the present disclosure has a COP ratio of 93.5% or more relative to that of R410A, and a GWP of 65 or less.

The refrigerant D according to the present disclosure is preferably a refrigerant wherein

when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC. CD, DA, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments CD and DA (excluding the points C and A);

-   -   the line segment CD is represented by coordinates         (−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and

the line segments OC, DA, and AO are straight lines. When the requirements above are satisfied, the refrigerant D according to the present disclosure has a COP ratio of 95% or more relative to that of R410A, and a GWP of 65 or less.

The refrigerant D according to the present disclosure may further comprise other additional refrigerants in addition to HFO-1132(E), HFO-1123, and R32, as long as the above properties and effects are not impaired. In this respect, the refrigerant D according to the present disclosure preferably comprises HFO-1132(E), HFO-1123, and R32 in a total amount of 99.5 mass % or more, more preferably 99.75 mass % or more, and even more preferably 99.9 mass % or more, based on the entire refrigerant D.

Such additional refrigerants are not limited, and can be selected from a wide range of refrigerants. The mixed refrigerant may comprise a single additional refrigerant, or two or more additional refrigerants.

The refrigerant D according to the present disclosure is suitable for use as an alternative refrigerant for R410A.

Examples of Refrigerant D

The refrigerant D is described in more detail below with reference to Examples. However, the refrigerant D according to the present disclosure is not limited to the Examples.

Mixed refrigerants were prepared by mixing HFO-1132(E), HFO-1123, and R32 at mass % based on their sum shown in Tables 24 to 26.

The COP ratio and the refrigerating capacity (which may be referred to as “cooling capacity” or “capacity”) ratio relative to those of R410 of the mixed refrigerants were determined. The conditions for calculation were as described below.

Evaporating temperature: 5° C. Condensation temperature: 45° C. Degree of superheating: 1 K Degree of subcooling: 5 K E_(comp) (compressive modulus): 0.7 kWh

Tables 24 to 26 show these values together with the GWP of each mixed refrigerant.

TABLE 24 Comp. Exam- Exam- Comp. Comp. Ex. 2 Exam- ple 2 Exam- ple 4 Ex. 3 Item Unit Ex. 1 C ple 1 D ple 3 E O HFO-1 132(E) mass % R410A 77.7 77.3 76.3 74.6 72.2 100.0 HFO-1123 mass % 22.3 17.7 14.2 11.4 9.4 0.0 R32 mass % 0.0 5.0 9.5 14.0 18.4 0.0 GWP — 2088 1 35 65 95 125 1 COP ratio % (relative 100.0 95.0 95.0 95.0 95.0 95.0 97.8 to R410A) Refrigerating % (relative 100.0 102.5 104.4 106.0 107.6 109.1 97.8 capacity ratio to R410A)

TABLE 25 Comp. Comp. Comp. Exam- Exam- Ex. Ex. Ex. 4 Exam- ple 6 Exam- ple 8 5 6 Item Unit C’ ple 5 D’ ple 7 E’ A B HFO- mass % 56.7 55.0 52.2 48.0 41.8 90.5 0.0 1132(E) HFO-1123 mass % 43.3 40.0 38.3 38.0 39.8 0.0 90.5 R32 mass % 0.0 5.0 9.5 14.0 18.4 9.5 9.5 GWP — 1 35 65 95 125 65 65 COP ratio % 92.5 92.5 92.5 92.5 92.5 96.6 90.8 (relative to R410A) Refrigerating % 105.8 107.9 109.7 111.5 113.2 103.2 111.0 capacity (relative ratio to R410A)

TABLE 26 Comp. Comp. Ex. Comp. Comp. Ex. 7 8 Exam- Exam- Exam- Ex. Ex. Item Unit A’ B’ ple 9 ple 10 ple 11 9 10 HFO- mass % 81.6 0.0 85.0 65.0 70.0 50.0 20.0 1132(E) HFO-1123 mass % 0.0 81.6 10.0 30.0 15.0 20.0 20.0 R32 mass % 18.4 18.4 5.0 5.0 15.0 30.0 60.0 GWP — 125 125 35 35 102 203 405 COP ratio % 95.9 91.9 95.9 93.6 94.6 94.3 97.6 (relative to R410A) Refrigerating % 107.4 113.8 102.9 106.5 108.7 114.6 117.6 capacity (relative ratio to R410A)

The results indicate that under the condition that the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum is respectively represented by x, y, and z, when coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure (FIG. 11 ) surrounded by line segments OC′, C′D′, D′E′, E′A′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), point E′ (41.8, 39.8, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments C′D′, D′E′, and E′A′ (excluding the points C′ and A′), the refrigerant has a COP ratio of 92.5% or more relative to that of R410A, and a GWP of 125 or less.

The results also indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 11 ) surrounded by line segments OC, CD, DE, EA′, and A′O that connect the following 5 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), point E (72.2, 9.4, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments CD, DE, and EA′ (excluding the points C and N), the refrigerant has a COP ratio of 95% or more relative to that of R410A, and a GWP of 125 or less.

The results also indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 11 ) surrounded by line segments OC′, C′D′, D′A, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments C′D′ and D′A (excluding the points C′ and A), the refrigerant has a COP ratio of 92.5% or more relative to that of R410A, and a GWP of 65 or less.

The results also indicate that when coordinates (x,y,z) are within the range of a figure (FIG. 11 ) surrounded by line segments OC, CD, DA, and AO that connect the following 4 points:

point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments CD and DA (excluding the points C and A), the refrigerant has a COP ratio of 95% or more relative to that of R410A, and a GWP of 65 or less.

In contrast, as shown in Comparative Examples 2, 3, and 4, when R32 is not contained, the concentrations of HFO-1132 and HFO-1123, which have a double bond, become relatively high; this undesirably leads to deterioration, such as decomposition, or polymerization in the refrigerant compound.

Moreover, as shown in Comparative Examples 3, 5, and 7, when HFO-1123 is not contained, the combustion-inhibiting effect thereof cannot be obtained; thus, undesirably, a composition having lower flammability cannot be obtained.

(2) Refrigerating Oil

A refrigerating oil as technique of second group can improve the lubricity in the refrigeration cycle apparatus and can also achieve efficient cycle performance by performing a refrigeration cycle such as a refrigeration cycle together with a refrigerant composition.

Examples of the refrigerating oil include oxygen-containing synthetic oils (e.g., ester-type refrigerating oils and ether-type refrigerating oils) and hydrocarbon refrigerating oils. In particular, ester-type refrigerating oils and ether-type refrigerating oils are preferred from the viewpoint of miscibility with refrigerants or refrigerant compositions. The refrigerating oils may be used alone or in combination of two or more.

The kinematic viscosity of the refrigerating oil at 40° C. is preferably 1 mm²/s or more and 750 mm²/s or less and more preferably 1 mm²/s or more and 400 mm²/s or less from at least one of the viewpoints of suppressing the deterioration of the lubricity and the hermeticity of compressors, achieving sufficient miscibility with refrigerants under low-temperature conditions, suppressing the lubrication failure of compressors, and improving the heat exchange efficiency of evaporators. Herein, the kinematic viscosity of the refrigerating oil at 100° C. may be, for example, 1 mm²/s or more and 100 mm²/s or less and is more preferably 1 mm²/s or more and 50 mm²/s or less.

The refrigerating oil preferably has an aniline point of −100° C. or higher and 0° C. or lower. The term “aniline point” herein refers to a numerical value indicating the solubility of, for example, a hydrocarbon solvent, that is, refers to a temperature at which when equal volumes of a sample (herein, refrigerating oil) and aniline are mixed with each other and cooled, turbidity appears because of their immiscibility (provided in JIS K 2256). Note that this value is a value of the refrigerating oil itself in a state in which the refrigerant is not dissolved. By using a refrigerating oil having such an aniline point, for example, even w % ben bearings constituting resin functional components and insulating materials for electric motors are used at positions in contact with the refrigerating oil, the suitability of the refrigerating oil for the resin functional components can be improved. Specifically, if the aniline point is excessively low, the refrigerating oil readily infiltrates the bearings and the insulating materials, and thus the bearings and the like tend to swell. On the other hand, if the aniline point is excessively high, the refrigerating oil does not readily infiltrate the bearings and the insulating materials, and thus the bearings and the like tend to shrink. Accordingly, the deformation of the bearings and the insulating materials due to swelling or shrinking can be prevented by using the refrigerating oil having an aniline point within the above-described predetermined range (−100° C. or higher and 0° C. or lower). If the bearings deform through swelling, the desired length of a gap at a sliding portion cannot be maintained. This may result in an increase in sliding resistance. If the bearings deform through shrinking, the hardness of the bearings increases, and consequently the bearings may be broken because of vibration of a compressor. In other words, the deformation of the bearings through shrinking may decrease the rigidity of the sliding portion. Furthermore, if the insulating materials (e.g., insulating coating materials and insulating films) of electric motors deform through swelling, the insulating properties of the insulating materials deteriorate. If the insulating materials deform through shrinking, the insulating materials may also be broken as in the case of the bearings, which also deteriorates the insulating properties. In contrast, when the refrigerating oil having an aniline point within the predetermined range is used as described above, the deformation of bearings and insulating materials due to swelling or shrinking can be suppressed, and thus such a problem can be avoided.

The refrigerating oil is used as a working fluid for a refrigerating machine by being mixed with a refrigerant composition. The content of the refrigerating oil relative to the whole amount of working fluid for a refrigerating machine is preferably 5 mass % or more and 60 mass % or less and more preferably 10 mass % or more and 50 mass % or less.

(2-1) Oxygen-Containing Synthetic Oil

An ester-type refrigerating oil or an ether-type refrigerating oil serving as an oxygen-containing synthetic oil is mainly constituted by carbon atoms and oxygen atoms. In the ester-type refrigerating oil or the ether-type refrigerating oil, an excessively low ratio (carbon/oxygen molar ratio) of carbon atoms to oxygen atoms increases the hygroscopicity, and an excessively high ratio of carbon atoms to oxygen atoms deteriorates the miscibility with a refrigerant. Therefore, the molar ratio is preferably 2 or more and 7.5 or less.

(2-1-1) Ester-Type Refrigerating Oil

Examples of base oil components of the ester-type refrigerating oil include dibasic acid ester oils of a dibasic acid and a monohydric alcohol, polyol ester oils of a polyol and a fatty acid, complex ester oils of a polyol, a polybasic acid, and a monohydric alcohol (or a fatty acid), and polyol carbonate oils from the viewpoint of chemical stability.

(Dibasic Acid Ester Oil)

The dibasic acid ester oil is preferably an ester of a dibasic acid such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, or terephthalic acid, in particular, a dibasic acid having 5 to 10 carbon atoms (e.g., glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid) and a monohydric alcohol having a linear or branched alkyl group and having 1 to 15 carbon atoms (e.g., methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, or pentadecanol). Specific examples of the dibasic acid ester oil include ditridecyl glutarate, di(2-ethylhexyl) adipate, diisodecyl adipate, ditridecyl adipate, and di(3-ethylhexyl) sebacate.

(Polyol Ester Oil)

The polyol ester oil is an ester synthesized from a polyhydric alcohol and a fatty acid (carboxylic acid), and has a carbon/oxygen molar ratio of 2 or more and 7.5 or less, preferably 3.2 or more and 5.8 or less.

The polyhydric alcohol constituting the polyol ester oil is a diol (e.g., ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, or 1,12-dodecanediol) or apolyol having 3 to 20 hydroxyl groups (trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), glycerol, polyglycerol (glycerol dimer or trimer), 1,3,5-pentanetriol, sorbitol, sorbitan, a sorbitol-glycerol condensate, a polyhydric alcohol such as adonitol, arabitol, xylitol, or mannitol, a saccharide such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, raffinose, gentianose, or melezitose, or a partially etherified product of the foregoing). One or two or more polyhydric alcohols may constitute an ester.

For the fatty acid constituting the polyol ester, the number of carbon atoms is not limited, but is normally 1 to 24. A linear fatty acid or a branched fatty acid is preferred. Examples of the linear fatty acid include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, oleic acid, linoleic acid, and linolenic acid. The hydrocarbon group that bonds to a carboxy group may have only a saturated hydrocarbon or may have an unsaturated hydrocarbon. Examples of the branched fatty acid include 2-methylpropionic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropionic acid, 2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2,3-trimethylbutanoic acid, 2,3,3-trimethylbutanoic acid, 2-ethyl-2-methylbutanoic acid, 2-ethyl-3-methylbutanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 4-ethylhexanoic acid, 2,2-dimethylhexanoic acid, 2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 2,5-dimethylhexanoic acid, 3,3-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 3,5-dimethylhexanoic acid, 4,4-dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 5,5-dimethylhexanoic acid, 2-propylpentanoic acid, 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid. 5-methyloctanoic acid, 6-methyloctanoic acid, 7-methyloctanoic acid, 2,2-dimethylheptanoic acid, 2,3-dimethylheptanoic acid, 2,4-dimethylheptanoic acid, 2,5-dimethylheptanoic acid, 2,6-dimethylheptanoic acid, 3,3-dimethylheptanoic acid, 3,4-dimethylheptanoic acid, 3,5-dimethylheptanoic acid, 3,6-dimethylheptanoic acid, 4,4-dimethylheptanoic acid, 4,5-dimethylheptanoic acid, 4,6-dimethylheptanoic acid, 5,5-dimethylheptanoic acid, 5,6-dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 2-methyl-2-ethylhexanoic acid, 2-methyl-3-ethylhexanoic acid, 2-methyl-4-ethylhexanoic acid, 3-methyl-2-ethylhexanoic acid, 3-methyl-3-ethylhexanoic acid, 3-methyl-4-ethylhexanoic acid, 4-methyl-2-ethylhexanoic acid, 4-methyl-3-ethylhexanoic acid, 4-methyl-4-ethylhexanoic acid, 5-methyl-2-ethylhexanoic acid, 5-methyl-3-ethylhexanoic acid, 5-methyl-4-ethylhexanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2,4,4-tetramethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, and 2,2-diisopropylpropanoic acid. One or two or more fatty acids selected from the foregoing may constitute an ester.

One polyhydric alcohol may be used to constitute an ester or a mixture of two or more polyhydric alcohols may be used to constitute an ester. The fatty acid constituting an ester may be a single component, or two or more fatty acids may constitute an ester. The fatty acids may be individual fatty acids of the same type or may be two or more types of fatty acids as a mixture. The polyol ester oil may have a free hydroxyl group.

Specifically, the polyol ester oil is more preferably an ester of a hindered alcohol such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), or tri-(pentaerythritol); further preferably an ester of neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, or di-(pentaerythritol); and preferably an ester of neopentyl glycol, trimethylolpropane, pentaerythritol, di-(pentaerythritol), or the like and a fatty acid having 2 to 20 carbon atoms.

The fatty acid constituting such a polyhydric alcohol fatty acid ester may be only a fatty acid having a linear alkyl group or may be selected from fatty acids having a branched structure. A mixed ester of linear and branched fatty acids may be employed. Furthermore, two or more fatty acids selected from the above fatty acids may be used to constitute an ester.

Specifically, for example, in the case of a mixed ester of linear and branched fatty acids, the molar ratio of a linear fatty acid having 4 to 6 carbon atoms and a branched fatty acid having 7 to 9 carbon atoms is 15:85 to 90:10, preferably 15:85 to 85:15, more preferably 20:80 to 80:20, further preferably 25:75 to 75:25, and most preferably 30:70 to 70:30. The total content of the linear fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms relative to the whole amount of fatty acid constituting the polyhydric alcohol fatty acid ester is preferably 20 mol % or more. The fatty acid preferably has such a composition that both of sufficient miscibility with a refrigerant and viscosity required as a refrigerating oil are achieved. The content of a fatty acid herein refers to a value relative to the whole amount of fatty acid constituting the polyhydric alcohol fatty acid ester contained in the refrigerating oil.

In particular, the refrigerating oil preferably contains an ester (hereafter referred to as a “polyhydric alcohol fatty acid ester (A)”) in which the molar ratio of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms is 15:85 to 90:10, the fatty acid having 4 to 6 carbon atoms contains 2-methylpropionic acid, and the total content of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms relative to the whole amount of fatty acid constituting the above ester is 20 mol % or more.

The polyhydric alcohol fatty acid ester (A) includes a complete ester in which all hydroxyl groups of a polyhydric alcohol are esterified, a partial ester in which some hydroxyl groups of a polyhydric alcohol are left without being esterified, and a mixture of a complete ester and a partial ester. The hydroxyl value of the polyhydric alcohol fatty acid ester (A) is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, and most preferably 3 mgKOH/g or less.

For the fatty acid constituting the polyhydric alcohol fatty acid ester (A), the molar ratio of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms is 15:85 to 90:10, preferably 15:85 to 85:15, more preferably 20:80 to 80:20, further preferably 25:75 to 75:25, and most preferably 30:70 to 70:30. The total content of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms relative to the whole amount of fatty acid constituting the polyhydric alcohol fatty acid ester (A) is 20 mol % or more. In the case where the above conditions for the composition of the fatty acid are not satisfied, if difluoromethane is contained in the refrigerant composition, both of sufficient miscibility with the difluoromethane and viscosity required as a refrigerating oil are not easily achieved at high levels. The content of a fatty acid refers to a value relative to the whole amount of fatty acid constituting the polyhydric alcohol fatty acid ester contained in the refrigerating oil.

Specific examples of the fatty acid having 4 to 6 carbon atoms include butanoic acid, 2-methylpropionic acid, pentanoic acid, 2-methylbutanoic acid. 3-methylbutanoic acid. 2,2-dimethylpropionic acid, 2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic acid, and hexanoic acid. Among them, a fatty acid having a branched structure at an alkyl skeleton, such as 2-methylpropionic acid, is preferred.

Specific examples of the branched fatty acid having 7 to 9 carbon atoms include 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 1,1,2-trimethylbutanoic acid, 1,2,2-trimethylbutanoic acid, 1-ethyl-1-methylbutanoic acid, 1-ethyl-2-methylbutanoic acid, octanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 3,5-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 2,2-dimethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid. 6-methylheptanoic acid, 2-propylpentanoic acid, nonanoic acid, 2,2-dimethylheptanoic acid, 2-methyloctanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2,4,4-tetramethylpentanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, and 2,2-diisopropylpropanoic acid.

The polyhydric alcohol fatty acid ester (A) may contain, as an acid constituent component, a fatty acid other than the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms as long as the molar ratio of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms is 15:85 to 90:10 and the fatty acid having 4 to 6 carbon atoms contains 2-methylpropionic acid.

Specific examples of the fatty acid other than the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms include fatty acids having 2 or 3 carbon atoms, such as acetic acid and propionic acid; linear fatty acids having 7 to 9 carbon atoms, such as heptanoic acid, octanoic acid, and nonanoic acid; and fatty acids having 10 to 20 carbon atoms, such as decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, and oleic acid.

When the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms are used in combination with fatty acids other than these fatty acids, the total content of the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms relative to the whole amount of fatty acid constituting the polyhydric alcohol fatty acid ester (A) is preferably 20 mol % or more, more preferably 25 mol % or more, and further preferably 30 mol % or more. When the content is 20 mol % or more, sufficient miscibility with difluoromethane is achieved in the case where the difluoromethane is contained in the refrigerant composition.

A polyhydric alcohol fatty acid ester (A) containing, as acid constituent components, only 2-methylpropionic acid and 3,5,5-trimethylhexanoic acid is particularly preferred from the viewpoint of achieving both necessary viscosity and miscibility with difluoromethane in the case where the difluoromethane is contained in the refrigerant composition.

The polyhydric alcohol fatty acid ester may be a mixture of two or more esters having different molecular structures. In this case, individual molecules do not necessarily satisfy the above conditions as long as the whole fatty acid constituting a pentaerythritol fatty acid ester contained in the refrigerating oil satisfies the above conditions.

As described above, the polyhydric alcohol fatty acid ester (A) contains the fatty acid having 4 to 6 carbon atoms and the branched fatty acid having 7 to 9 carbon atoms as essential acid components constituting the ester and may optionally contain other fatty acids as constituent components. In other words, the polyhydric alcohol fatty acid ester (A) may contain only two fatty acids as acid constituent components or three or more fatty acids having different structures as acid constituent components, but the polyhydric alcohol fatty acid ester preferably contains, as an acid constituent component, only a fatty acid whose carbon atom (α-position carbon atom) adjacent to carbonyl carbon is not quaternary carbon. If the fatty acid constituting the polyhydric alcohol fatty acid ester contains a fatty acid whose α-position carbon atom is quaternary carbon, the lubricity in the presence of difluoromethane in the case where the difluoromethane is contained in the refrigerant composition tends to be insufficient.

The polyhydric alcohol constituting the polyol ester according to this embodiment is preferably a polyhydric alcohol having 2 to 6 hydroxyl groups.

Specific examples of the dihydric alcohol (diol) include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol. Specific examples of the trihydric or higher alcohol include polyhydric alcohols such as trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), tri-(pentaerythritol), glycerol, polyglycerol (glycerol dimer or trimer), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerol condensates, adonitol, arabitol, xylitol, and mannitol; saccharides such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, and cellobiose; and partially etherified products of the foregoing. Among them, in terms of better hydrolysis stability, an ester of a hindered alcohol such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, di-(trimethylolpropane), tri-(trimethylolpropane), pentaerythritol, di-(pentaerythritol), or tri-(pentaerythritol) is preferably used; an ester of neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, or di-(pentaerythritol) is more preferably used; and neopentyl glycol, trimethylolpropane, pentaerythritol, or di-(pentaerythritol) is further preferably used. In terms of excellent miscibility with a refrigerant and excellent hydrolysis stability, a mixed ester of pentaerythritol, di-(pentaerythritol), or pentaerythritol and di-(pentaerythritol) is most preferably used.

Preferred examples of the acid constituent component constituting the polyhydric alcohol fatty acid ester (A) are as follows:

(i) a combination of 1 to 13 acids selected from butanoic acid, 2-methylpropionic acid, pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropionic acid, 2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic acid, and hexanoic acid and 1 to 13 acids selected from 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, and 2-ethyl-3-methylbutanoic acid; (ii) a combination of 1 to 13 acids selected from butanoic acid, 2-methylpropionic acid, pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid. 2,2-dimethylpropionic acid, 2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic acid, and hexanoic acid and 1 to 25 acids selected from 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid, 2,2-dimethylhexanoic acid, 3,3-dimethylhexanoic acid, 4,4-dimethylhexanoic acid, 5,5-dimethylhexanoic acid, 2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 2,5-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 3,5-dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 2,2,3-trimethylpentanoic acid, 2,3,3-trimethylpentanoic acid, 2,4,4-trimethylpentanoic acid, 3,4,4-trimethylpentanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 2-propylpentanoic acid, 2-methyl-2-ethylpentanoic acid, 2-methyl-3-ethylpentanoic acid, and 3-methyl-3-ethylpentanoic acid, and (iii) a combination of 1 to 13 acids selected from butanoic acid, 2-methylpropionic acid, pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropionic acid, 2-methylpentanoic acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2,2-dimethylbutanoic acid, 2,3-dimethylbutanoic acid, 3,3-dimethylbutanoic acid, and hexanoic acid and 1 to 50 acids selected from 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 7-methyloctanoic acid, 8-methyloctanoic acid, 2,2-dimethylheptanoic acid, 3,3-dimethylheptanoic acid, 4,4-dimethylheptanoic acid, 5,5-dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 2,3-dimethylheptanoic acid, 2,4-dimethylheptanoic acid, 2,5-dimethylheptanoic acid, 2,6-dimethylheptanoic acid, 3,4-dimethylheptanoic acid, 3,5-dimethylheptanoic acid, 3,6-dimethylheptanoic acid, 4,5-dimethylheptanoic acid, 4,6-dimethylheptanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 5-ethylheptanoic acid, 2-propylhexanoic acid, 3-propylhexanoic acid, 2-butylpentanoic acid, 2,2,3-trimethylhexanoic acid, 2,2,3-trimethylhexanoic acid, 2,2,4-trimethylhexanoic acid, 2,2,5-trimethylhexanoic acid, 2,3,4-trimethylhexanoic acid, 2,3,5-trimethylhexanoic acid, 3,3,4-trimethylhexanoic acid, 3,3,5-trimethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 4,4,5-trimethylhexanoic acid, 4,5,5-trimethylhexanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,2,4,4-tetramethylpentanoic acid, 2,3,4,4-tetramethylpentanoic acid, 3,3,4,4-tetramethylpentanoic acid, 2,2-diethylpentanoic acid. 2,3-diethylpentanoic acid, 3,3-diethylpentanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 3-ethyl-2,2,3-trimethylbutyric acid, and 2,2-diisopropylpropionic acid.

Further preferred examples of the acid constituent component constituting the polyhydric alcohol fatty acid ester are as follows:

(i) a combination of 2-methylpropionic acid and 1 to 13 acids selected from 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, and 2-ethyl-3-methylbutanoic acid; (ii) a combination of 2-methylpropionic acid and 1 to 25 acids selected from 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid, 2,2-dimethylhexanoic acid, 3,3-dimethylhexanoic acid, 4,4-dimethylhexanoic acid, 5,5-dimethylhexanoic acid, 2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 2,5-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 3,5-dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 2,2,3-trimethylpentanoic acid, 2,3,3-trimethylpentanoic acid, 2,4,4-trimethylpentanoic acid, 3,4,4-trimethylpentanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 2-propylpentanoic acid, 2-methyl-2-ethylpentanoic acid, 2-methyl-3-ethylpentanoic acid, and 3-methyl-3-ethylpentanoic acid; and (iii) a combination of 2-methylpropionic acid and 1 to 50 acids selected from 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 7-methyloctanoic acid, 8-methyloctanoic acid, 2,2-dimethylheptanoic acid, 3,3-dimethylheptanoic acid, 4,4-dimethylheptanoic acid, 5,5-dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 2,3-dimethylheptanoic acid, 2,4-dimethylheptanoic acid, 2,5-dimethylheptanoic acid, 2,6-dimethylheptanoic acid, 3,4-dimethylheptanoic acid, 3,5-dimethylheptanoic acid, 3,6-dimethylheptanoic acid, 4,5-dimethylheptanoic acid, 4,6-dimethylheptanoic acid, 2-ethylheptanoic acid, 3-ethylheptanoic acid, 4-ethylheptanoic acid, 5-ethylheptanoic acid, 2-propylhexanoic acid, 3-propylhexanoic acid, 2-butylpentanoic acid, 2,2,3-trimethylhexanoic acid, 2,2,3-trimethylhexanoic acid, 2,2,4-trimethylhexanoic acid, 2,2,5-trimethylhexanoic acid, 2,3,4-trimethylhexanoic acid, 2,3,5-trimethylhexanoic acid, 3,3,4-trimethylhexanoic acid, 3,3,5-trimethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 4,4,5-trimethylhexanoic acid, 4,5,5-trimethylhexanoic acid, 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,2,4,4-tetramethylpentanoic acid, 2,3,4,4-tetramethylpentanoic acid, 3,3,4,4-tetramethylpentanoic acid, 2,2-diethylpentanoic acid, 2,3-diethylpentanoic acid, 3,3-diethylpentanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 3-ethyl-2,2,3-trimethylbutyric acid, and 2,2-diisopropylpropionic acid.

The content of the polyhydric alcohol fatty acid ester (A) is 50 mass % or more, preferably 60 mass % or more, more preferably 70 mass % or more, and further preferably 75 mass % or more relative to the whole amount of the refrigerating oil. The refrigerating oil according to this embodiment may contain a lubricating base oil other than the polyhydric alcohol fatty acid ester (A) and additives as described later. However, if the content of the polyhydric alcohol fatty acid ester (A) is less than 50 mass %, necessary viscosity and miscibility cannot be achieved at high levels.

In the refrigerating oil according to this embodiment, the polyhydric alcohol fatty acid ester (A) is mainly used as a base oil. The base oil of the refrigerating oil according to this embodiment may be a polyhydric alcohol fatty acid ester (A) alone (i.e., the content of the polyhydric alcohol fatty acid ester (A) is 100 mass %). However, in addition to the polyhydric alcohol fatty acid ester (A), a base oil other than the polyhydric alcohol fatty acid ester (A) may be further contained to the degree that the excellent performance of the polyhydric alcohol fatty acid ester (A) is not impaired. Examples of the base oil other than the polyhydric alcohol fatty acid ester (A) include hydrocarbon oils such as mineral oils, olefin polymers, alkyldiphenylalkanes, alkylnaphthalenes, and alkylbenzenes; and esters other than the polyhydric alcohol fatty acid ester (A), such as polyol esters, complex esters, and alicyclic dicarboxylic acid esters, and oxygen-containing synthetic oils (hereafter, may be referred to as “other oxygen-containing synthetic oils”) such as polyglycols, polyvinyl ethers, ketones, polyphenyl ethers, silicones, polysiloxanes, and perfluoroethers.

Among them, the oxygen-containing synthetic oil is preferably an ester other than the polyhydric alcohol fatty acid ester (A), a polyglycol, or a polyvinyl ether and particularly preferably a polyol ester other than the polyhydric alcohol fatty acid ester (A). The polyol ester other than the polyhydric alcohol fatty acid ester (A) is an ester of a fatty acid and a polyhydric alcohol such as neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, or dipentaerythritol and is particularly preferably an ester of neopentyl glycol and a fatty acid, an ester of pentaerythritol and a fatty acid, or an ester of dipentaerythritol and a fatty acid.

The neopentyl glycol ester is preferably an ester of neopentyl glycol and a fatty acid having 5 to 9 carbon atoms. Specific examples of the neopentyl glycol ester include neopentyl glycol di(3,5,5-trimethylhexanoate), neopentyl glycol di(2-ethylhexanoate), neopentyl glycol di(2-methylhexanoate), neopentyl glycol di(2-ethylpentanoate), an ester of neopentyl glycol and 2-methylhexanoic acid-2-ethylpentanoic acid, an ester of neopentyl glycol and 3-methylhexanoic acid-5-methylhexanoic acid, an ester of neopentyl glycol and 2-methylhexanoic acid-2-ethylhexanoic acid, an ester of neopentyl glycol and 3,5-dimethylhexanoic acid, 4,5-dimethylhexanoic acid-3,4-dimethylhexanoic acid, neopentyl glycol dipentanoate, neopentyl glycol di(2-ethylbutanoate), neopentyl glycol di(2-methylpentanoate), neopentyl glycol di(2-methylbutanoate), and neopentyl glycol di(3-methylbutanoate).

The pentaerythritol ester is preferably an ester of pentaerythritol and a fatty acid having 5 to 9 carbon atoms. The pentaerythritol ester is, specifically, an ester of pentaerythritol and at least one fatty acid selected from pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, hexanoic acid, 2-methylpentanoic acid, 2-ethylbutanoic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid, 3,5,5-trimethylhexanoic acid, and 2-ethylhexanoic acid.

The dipentaerythritol ester is preferably an ester of dipentaerythritol and a fatty acid having 5 to 9 carbon atoms. The dipentaerythritol ester is, specifically, an ester of dipentaerythritol and at least one fatty acid selected from pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, hexanoic acid, 2-methylpentanoic acid, 2-ethylbutanoic acid, 2-ethylpentanoic acid, 2-methylhexanoic acid. 3,5,5-trimethylhexanoic acid, and 2-ethylhexanoic acid.

When the refrigerating oil according to this embodiment contains an oxygen-containing synthetic oil other than the polyhydric alcohol fatty acid ester (A), the content of the oxygen-containing synthetic oil other than the polyhydric alcohol fatty acid ester (A) is not limited as long as excellent lubricity and miscibility of the refrigerating oil according to this embodiment are not impaired. When a polyol ester other than the polyhydric alcohol fatty acid ester (A) is contained, the content of the polyol ester is preferably less than 50 mass %, more preferably 45 mass % or less, still more preferably 40 mass % or less, even more preferably 35 mass % or less, further preferably 30 mass % or less, and most preferably 25 mass % or less relative to the whole amount of the refrigerating oil. When an oxygen-containing synthetic oil other than the polyol ester is contained, the content of the oxygen-containing synthetic oil is preferably less than 50 mass %, more preferably 40 mass % or less, and further preferably 30 mass % or less relative to the whole amount of the refrigerating oil. If the content of the polyol ester other than the pentaerythritol fatty acid ester or the oxygen-containing synthetic oil is excessively high, the above-described effects are not sufficiently produced.

The polyol ester other than the polyhydric alcohol fatty acid ester (A) may be a partial ester in which some hydroxyl groups of a polyhydric alcohol are left without being esterified, a complete ester in which all hydroxyl groups are esterified, or a mixture of a partial ester and a complete ester. The hydroxyl value is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, and most preferably 3 mgKOH/g or less.

When the refrigerating oil and the working fluid for a refrigerating machine according to this embodiment contain a polyol ester other than the polyhydric alcohol fatty acid ester (A), the polyol ester may contain one polyol ester having a single structure or a mixture of two or more polyol esters having different structures.

The polyol ester other than the polyhydric alcohol fatty acid ester (A) may be any of an ester of one fatty acid and one polyhydric alcohol, an ester of two or more fatty acids and one polyhydric alcohol, an ester of one fatty acid and two or more polyhydric alcohols, and an ester of two or more fatty acids and two or more polyhydric alcohols.

The refrigerating oil according to this embodiment may be constituted by only the polyhydric alcohol fatty acid ester (A) or by the polyhydric alcohol fatty acid ester (A) and other base oils. The refrigerating oil may further contain various additives described later. The working fluid for a refrigerating machine according to this embodiment may also further contain various additives. In the following description, the content of additives is expressed relative to the whole amount of the refrigerating oil, but the content of these components in the working fluid for a refrigerating machine is desirably determined so that the content is within the preferred range described later when expressed relative to the whole amount of the refrigerating oil.

To further improve the abrasion resistance and load resistance of the refrigerating oil and the working fluid for a refrigerating machine according to this embodiment, at least one phosphorus compound selected from the group consisting of phosphoric acid esters, acidic phosphoric acid esters, thiophosphoric acid esters, amine salts of acidic phosphoric acid esters, chlorinated phosphoric acid esters, and phosphorous acid esters can be added. These phosphorus compounds are esters of phosphoric acid or phosphorous acid and alkanol or polyether-type alcohol, or derivatives thereof.

Specific examples of the phosphoric acid ester include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyldiphenyl phosphate, and xylenyldiphenyl phosphate.

Examples of the acidic phosphoric acid ester include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate.

Examples of the thiophosphoric acid ester include tributyl phosphorothionate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothionate, tridecyl phosphorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, trihexadecyl phosphorothionate, triheptadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothionate, trixylenyl phosphorothionate, cresyldiphenyl phosphorothionate, and xylenyldiphenyl phosphorothionate.

The amine salt of an acidic phosphoric acid ester is an amine salt of an acidic phosphoric acid ester and a primary, secondary, or tertiary amine that has a linear or branched alkyl group and that has 1 to 24 carbon atoms, preferably 5 to 18 carbon atoms.

For the amine constituting the amine salt of an acidic phosphoric acid ester, the amine salt is a salt of an amine such as a linear or branched methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, oleylamine, tetracosylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dihexadecylamine, diheptadecylamine, dioctadecylamine, dioleylamine, ditetracosylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, tridodecylamine, tritridecylamine, tritetradecylamine, tripentadecylamine, trihexadecylamine, triheptadecylamine, trioctadecylamine, trioleylamine, or tritetracosylamine. The amine may be a single compound or a mixture of two or more compounds.

Examples of the chlorinated phosphoric acid ester include tris(dichloropropyl) phosphate, tris(chloroethyl) phosphate, tris(chlorophenyl) phosphate, and polyoxyalkylene-bis[di(chloroaklyl)] phosphate. Examples of the phosphorous acid ester include dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, and tricresyl phosphite. Mixtures of these compounds can also be used.

When the refrigerating oil and the working fluid for a refrigerating machine according to this embodiment contain the above-described phosphorus compound, the content of the phosphorus compound is not limited, but is preferably 0.01 to 5.0 mass % and more preferably 0.02 to 3.0 mass % relative to the whole amount of the refrigerating oil (relative to the total amount of the base oil and all the additives). The above-described phosphorus compounds may be used alone or in combination of two or more.

The refrigerating oil and the working fluid for a refrigerating machine according to this embodiment may contain a terpene compound to further improve the thermal and chemical stability. The “terpene compound” in the present invention refers to a compound obtained by polymerizing isoprene and a derivative thereof, and a dimer to an octamer of isoprene are preferably used. Specific examples of the terpene compound include monoterpenes such as geraniol, nerol, linalool, citral (including geranial), citronellol, menthol, limonene, terpinerol, carvone, ionone, thujone, camphor, and bomeol; sesquiterpenes such as farnesene, farnesol, nerolidol, juvenile hormone, humulene, caryophyllene, elemene, cadinol, cadinene, and tutin; diterpenes such as geranylgeraniol, phytol, abietic acid, pimaragen, daphnetoxin, taxol, and pimaric acid; sesterterpenes such as geranylfarnesene; triterpenes such as squalene, limonin, camelliagenin, hopane, and lanosterol; and tetraterpenes such as carotenoid.

Among these terpene compounds, the terpene compound is preferably monoterpene, sesquiterpene, or diterpene, more preferably sesquiterpene, and particularly preferably α-farnesene (3,7,11-trimethyldodeca-1,3,6,10-tetraene) and/or β-farnesene (7,11-dimethyl-3-methylidenedodeca-1,6,10-triene). In the present invention, the terpene compounds may be used alone or in combination of two or more.

The content of the terpene compound in the refrigerating oil according to this embodiment is not limited, but is preferably 0.001 to 10 mass %, more preferably 0.01 to 5 mass %, and further preferably 0.05 to 3 mass % relative to the whole amount of the refrigerating oil. If the content of the terpene compound is less than 0.001 mass %, an effect of improving the thermal and chemical stability tends to be insufficient. If the content is more than 10 mass %, the lubricity tends to be insufficient. The content of the terpene compound in the working fluid for a refrigerating machine according to this embodiment is desirably determined so that the content is within the above preferred range when expressed relative to the whole amount of the refrigerating oil.

The refrigerating oil and the working fluid for a refrigerating machine according to this embodiment may contain at least one epoxy compound selected from phenyl glycidyl ether-type epoxy compounds, alkyl glycidyl ether-type epoxy compounds, glycidyl ester-type epoxy compounds, allyloxirane compounds, alkyloxirane compounds, alicyclic epoxy compounds, epoxidized fatty acid monoesters, and epoxidized vegetable oils to further improve the thermal and chemical stability.

Specific examples of the phenyl glycidyl ether-type epoxy compound include phenyl glycidyl ether and alkylphenyl glycidyl ethers. The alkylphenyl glycidyl ether herein is an alkylphenyl glycidyl ether having 1 to 3 alkyl groups with 1 to 13 carbon atoms. In particular, the alkylphenyl glycidyl ether is preferably an alkylphenyl glycidyl ether having one alkyl group with 4 to 10 carbon atoms, such as n-butylphenyl glycidyl ether, i-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, pentylphenyl glycidyl ether, hexylphenyl glycidyl ether, heptylphenyl glycidyl ether, octylphenyl glycidyl ether, nonylphenyl glycidyl ether, or decylphenyl glycidyl ether.

Specific examples of the alkyl glycidyl ether-type epoxy compound include decyl glycidyl ether, undecyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, 2-ethylhexyl glycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, polyalkylene glycol monoglycidyl ether, and polyalkylene glycol diglycidyl ether.

Specific examples of the glycidyl ester-type epoxy compound include phenyl glycidyl ester, alkyl glycidyl esters, and alkenyl glycidyl esters. Preferred examples of the glycidyl ester-type epoxy compound include glycidyl-2,2-dimethyloctanoate, glycidyl benzoate, glycidyl acrylate, and glycidyl methacrylate.

Specific examples of the allyloxirane compound include 1,2-epoxystyrene and alkyl-1,2-epoxystyrenes.

Specific examples of the alkyloxirane compound include 1,2-epoxybutane, 1,2-epoxypentane. 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,1,2-epoxyoctadecane, 2-epoxynonadecane, and 1,2-epoxyeicosane.

Specific examples of the alicyclic epoxy compound include 1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, bis(3,4-epoxycyclohexylmethyl) adipate, exo-2,3-epoxynorbornane, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, 2-(7-oxabicyclo[4.1.0]hept-3-yl)-spiro(1,3-dioxane-5,3′-[7]oxabicyclo[4.1.0]heptane. 4-(1′-methylepoxyethyl)-1,2-epoxy-2-methylcyclohexane, and 4-epoxyethyl-1,2-epoxycyclohexane.

Specific examples of the epoxidized fatty acid monoester include esters of an epoxidized fatty acid having 12 to 20 carbon atoms and an alcohol having 1 to 8 carbon atoms, phenol, or an alkylphenol. In particular, butyl, hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl, and butyl phenyl esters of epoxystearic acid are preferably used.

Specific examples of the epoxidized vegetable oil include epoxy compounds of vegetable oils such as soybean oil, linseed oil, and cottonseed oil.

Among these epoxy compounds, phenyl glycidyl ether-type epoxy compounds, alkyl glycidyl ether-type epoxy compounds, glycidyl ester-type epoxy compounds, and alicyclic epoxy compounds are preferred.

When the refrigerating oil and the working fluid for a refrigerating machine according to this embodiment contain the above-described epoxy compound, the content of the epoxy compound is not limited, but is preferably 0.01 to 5.0 mass % and more preferably 0.1 to 3.0 mass % relative to the whole amount of the refrigerating oil. The above-described epoxy compounds may be used alone or in combination of two or more.

The kinematic viscosity of the refrigerating oil containing the polyhydric alcohol fatty acid ester (A) at 40° C. is preferably 20 to 80 mm²/s, more preferably 25 to 75 mm²/s, and most preferably 30 to 70 mm²/s. The kinematic viscosity at 100° C. is preferably 2 to 20 mm²/s and more preferably 3 to 10 mm²/s. When the kinematic viscosity is more than or equal to the lower limit, the viscosity required as a refrigerating oil is easily achieved. On the other hand, when the kinematic viscosity is less than or equal to the upper limit, sufficient miscibility with difluoromethane in the case where the difluoromethane is contained as a refrigerant composition can be achieved.

The volume resistivity of the refrigerating oil containing the polyhydric alcohol fatty acid ester (A) is not limited, but is preferably 1.0×10¹²Ω·cm or more, more preferably 1.0×10¹³Ω·cm or more, and most preferably 1.0×10¹⁴Ω·cm or more. In particular, when the refrigerating oil is used for sealed refrigerating machines, high electric insulation tends to be required. The volume resistivity refers to a value measured at 25° C. in conformity with JIS C 2101 “Testing methods of electrical insulating oils”.

The water content of the refrigerating oil containing the polyhydric alcohol fatty acid ester (A) is not limited, but is preferably 200 ppm or less, more preferably 100 ppm or less, and most preferably 50 ppm or less relative to the whole amount of the refrigerating oil. In particular, when the refrigerating oil is used for sealed refrigerating machines, the water content needs to be low from the viewpoints of the thermal and chemical stability of the refrigerating oil and the influence on electric insulation.

The acid number of the refrigerating oil containing the polyhydric alcohol fatty acid ester (A) is not limited, but is preferably 0.1 mgKOH/g or less and more preferably 0.05 mgKOH/g or less to prevent corrosion of metals used for refrigerating machines or pipes. In the present invention, the acid number refers to an acid number measured in conformity with JIS K 2501 “Petroleum products and lubricants—Determination of neutralization number”.

The ash content of the refrigerating oil containing the polyhydric alcohol fatty acid ester (A) is not limited, but is preferably 100 ppm or less and more preferably 50 ppm or less to improve the thermal and chemical stability of the refrigerating oil and suppress the generation of sludge and the like. The ash content refers to an ash content measured in conformity with JIS K 2272 “Crude oil and petroleum products—Determination of ash and sulfated ash”.

(Complex Ester Oil)

The complex ester oil is an ester of a fatty acid and a dibasic acid, and a monohydric alcohol and a polyol. The above-described fatty acid, dibasic acid, monohydric alcohol, and polyol can be used.

Examples of the fatty acid include the fatty acids mentioned in the polyol ester.

Examples of the dibasic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid.

Examples of the polyol include the polyhydric alcohols in the polyol ester. The complex ester is an ester of such a fatty acid, dibasic acid, and polyol, each of which may be constituted by a single component or a plurality of components.

(Polyol Carbonate Oil)

The polyol carbonate oil is an ester of a carbonic acid and a polyol.

Examples of the polyol include the above-described diols and polyols.

The polyol carbonate oil may be a ring-opened polymer of a cyclic alkylene carbonate.

(2-1-2) Ether-Type Refrigerating Oil

The ether-type refrigerating oil is, for example, a polyvinyl ether oil or a polyoxyalkylene oil.

(Polyvinyl Ether Oil)

Examples of the polyvinyl ether oil include polymers of a vinyl ether monomer, copolymers of a vinyl ether monomer and a hydrocarbon monomer having an olefinic double bond, and copolymers of a monomer having an olefinic double bond and a polyoxyalkylene chain and a vinyl ether monomer.

The carbon/oxygen molar ratio of the polyvinyl ether oil is preferably 2 or more and 7.5 or less and more preferably 2.5 or more and 5.8 or less. If the carbon/oxygen molar ratio is smaller than the above range, the hygroscopicity increases. If the carbon/oxygen molar ratio is larger than the above range, the miscibility deteriorates. The weight-average molecular weight of the polyvinyl ether is preferably 200 or more and 3000 or less and more preferably 500 or more and 1500 or less.

The pour point of the polyvinyl ether oil is preferably −30° C. or lower. The surface tension of the polyvinyl ether oil at 20° C. is preferably 0.02 N/m or more and 0.04 N/m or less. The density of the polyvinyl ether oil at 15° C. is preferably 0.8 g/cm³ or more and 1.8 g/cm³ or less. The saturated water content of the polyvinyl ether oil at a temperature of 30° C., and a relative humidity of 90% is preferably 2000 ppm or more.

The refrigerating oil may contain polyvinyl ether as a main component. In the case where HFO-1234yf is contained as a refrigerant, the polyvinyl ether serving as a main component of the refrigerating oil has miscibility with HFO-1234yf. When the refrigerating oil has a kinematic viscosity at 40° C. of 400 mm²/s or less, HFO-1234yf is dissolved in the refrigerating oil to some extent. When the refrigerating oil has a pour point of −30° C. or lower, the flowability of the refrigerating oil is easily ensured even at positions at which the temperature of the refrigerant composition and the refrigerating oil is low in the refrigerant circuit. When the refrigerating oil has a surface tension at 20° C. of 0.04 N/m or less, the refrigerating oil discharged from a compressor does not readily form large droplets of oil that are not easily carried away by a refrigerant composition. Therefore, the refrigerating oil discharged from the compressor is dissolved in HFO-1234yf and is easily returned to the compressor together with HFO-1234yf.

When the refrigerating oil has a kinematic viscosity at 40° C. of 30 mm²/s or more, an insufficient oil film strength due to excessively low kinematic viscosity is suppressed, and thus good lubricity is easily achieved. When the refrigerating oil has a surface tension at 20° C. of 0.02 N/m or more, the refrigerating oil does not readily form small droplets of oil in a gas refrigerant inside the compressor, which can suppress discharge of a large amount of refrigerating oil from the compressor. Therefore, a sufficient amount of refrigerating oil is easily stored in the compressor.

When the refrigerating oil has a saturated water content at 30° C./90% RH of 2000 ppm or more, a relatively high hygroscopicity of the refrigerating oil can be achieved. Thus, when HFO-1234yf is contained as a refrigerant, water in HFO-1234yf can be captured by the refrigerating oil to some extent. HFO-1234yf has a molecular structure that is easily altered or deteriorated because of the influence of water contained. Therefore, the hydroscopic effects of the refrigerating oil can suppress such deterioration.

Furthermore, when a particular resin functional component is disposed in the sealing portion or sliding portion that is in contact with a refrigerant flowing through the refrigerant circuit and the resin functional component is formed of any of polytetrafluoroethylene, polyphenylene sulfide, phenolic resin, polyamide resin, chloroprene rubber, silicon rubber, hydrogenated nitrile rubber, fluororubber, and hydrin rubber, the aniline point of the refrigerating oil is preferably set within a particular range in consideration of the adaptability with the resin functional component. By setting the aniline point in such a manner, for example, the adaptability of bearings constituting the resin functional component with the refrigerating oil is improved. Specifically, if the aniline point is excessively low, the refrigerating oil readily infiltrates bearings or the like, and the bearings or the like readily swell. On the other hand, if the aniline point is excessively high, the refrigerating oil does not readily infiltrate bearings or the like, and the bearings or the like readily shrink. Therefore, by setting the aniline point of the refrigerating oil within a particular range, the swelling or shrinking of the bearings or the like can be prevented. Herein, for example, if each of the bearings or the like deforms through swelling or shrinking, the desired length of a gap at a sliding portion cannot be maintained. This may increase the sliding resistance or decrease the rigidity of the sliding portion. However, when the aniline point of the refrigerating oil is set within a particular range as described above, the deformation of the bearings or the like through swelling or shrinking is suppressed, and thus such a problem can be avoided.

The vinyl ether monomers may be used alone or in combination of two or more. Examples of the hydrocarbon monomer having an olefinic double bond include ethylene, propylene, various butenes, various pentenes, various hexenes, various heptenes, various octenes, diisobutylene, triisobutylene, styrene, α-methylstyrene, and various alkyl-substituted styrenes. The hydrocarbon monomers having an olefinic double bond may be used alone or in combination of two or more.

The polyvinyl ether copolymer may be a block copolymer or a random copolymer. The polyvinyl ether oils may be used alone or in combination of two or more.

A polyvinyl ether oil preferably used has a structural unit represented by general formula (1) below.

(In the formula, R¹, R², and R³ may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R⁴ represents a divalent hydrocarbon group having 1 to 10 carbon atoms or an ether bond oxygen-containing divalent hydrocarbon group having 2 to 20 carbon atoms, R⁵ represents a hydrocarbon group having 1 to 20 carbon atoms, m represents a number at which the average of m in the polyvinyl ether is 0 to 10, R¹ to R⁵ may be the same or different in each of structural units, and when m represents 2 or more in one structural unit, a plurality of R⁴O may be the same or different.)

At least one of R¹, R², and R³ in the general formula (1) preferably represents a hydrogen atom. In particular, all of R¹, R², and R³ preferably represent a hydrogen atom. In the general formula (1), m preferably represents 0 or more and 10 or less, particularly preferably 0 or more and 5 or less, further preferably 0. R⁵ in the general formula (1) represents a hydrocarbon group having 1 to 20 carbon atoms. Specific examples of the hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, and various octyl groups; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, various methylcyclohexyl groups, various ethylcyclohexyl groups, and various dimethylcyclohexyl groups: aryl groups such as a phenyl group, various methylphenyl groups, various ethylphenyl groups, and various dimethylphenyl groups; and arylalkyl groups such as a benzyl group, various phenylethyl groups, and various methylbenzyl groups. Among the alkyl groups, the cycloalkyl groups, the phenyl group, the aryl groups, and the arylalkyl groups, alkyl groups, in particular, alkyl groups having 1 to 5 carbon atoms are preferred. For the polyvinyl ether oil contained, the ratio of a polyvinyl ether oil with R⁵ representing an alkyl group having 1 or 2 carbon atoms and a polyvinyl ether oil with R representing an alkyl group having 3 or 4 carbon atoms is preferably 40%:60% to 100%:0%.

The polyvinyl ether oil according to this embodiment may be a homopolymer constituted by the same structural unit represented by the general formula (1) or a copolymer constituted by two or more structural units. The copolymer may be a block copolymer or a random copolymer.

The polyvinyl ether oil according to this embodiment may be constituted by only the structural unit represented by the general formula (1) or may be a copolymer further including a structural unit represented by general formula (2) below. In this case, the copolymer may be a block copolymer or a random copolymer.

(In the formula, R⁶ to R⁹ may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)

The vinyl ether monomer is, for example, a compound represented by general formula (3) below.

(In the formula. R¹, R², R³, R⁴, R⁵, and m have the same meaning as R¹, R², R³, R⁴, R⁵, and m in the general formula (1), respectively.)

Examples of various polyvinyl ether compounds corresponding to the above polyvinyl ether compound include vinyl methyl ether; vinyl ethyl ether; vinyl-n-propyl ether; vinyl-isopropyl ether; vinyl-n-butyl ether; vinyl-isobutyl ether; vinyl-sec-butyl ether; vinyl-tert-butyl ether; vinyl-n-pentyl ether; vinyl-n-hexyl ether; vinyl-2-methoxyethyl ether; vinyl-2-ethoxyethyl ether; vinyl-2-methoxy-1-methylethyl ether; vinyl-2-methoxy-propyl ether; vinyl-3,6-dioxaheptyl ether; vinyl-3,6,9-trioxadecyl ether; vinyl-1,4-dimethyl-3,6-dioxaheptyl ether; vinyl-1,4,7-trimethyl-3,6,9-trioxadecyl ether; vinyl-2,6-dioxa-4-heptyl ether; vinyl-2,6,9-trioxa-4-decyl ether; 1-methoxypropene; 1-ethoxypropene; 1-n-propoxypropene; 1-isopropoxypropene; 1-n-butoxypropene; 1-isobutoxypropene; 1-sec-butoxypropene; 1-tert-butoxypropene; 2-methoxypropene; 2-ethoxypropene; 2-n-propoxypropene; 2-isopropoxypropene; 2-n-butoxypropene; 2-isobutoxypropene; 2-sec-butoxypropene; 2-tert-butoxypropene; 1-methoxy-1-butene; 1-ethoxy-1-butene; 1-n-propoxy-1-butene; 1-isopropoxy-1-butene; 1-n-butoxy-1-butene; 1-isobutoxy-1-butene; 1-sec-butoxy-1-butene; 1-tert-butoxy-1-butene; 2-methoxy-1-butene; 2-ethoxy-1-butene; 2-n-propoxy-1-butene; 2-isopropoxy-1-butene; 2-n-butoxy-1-butene; 2-isobutoxy-1-butene; 2-sec-butoxy-1-butene; 2-tert-butoxy-1-butene; 2-methoxy-2-butene; 2-ethoxy-2-butene; 2-n-propoxy-2-butene; 2-isopropoxy-2-butene; 2-n-butoxy-2-butene; 2-isobutoxy-2-butene; 2-sec-butoxy-2-butene; and 2-tert-butoxy-2-butene. These vinyl ether monomers can be produced by a publicly known method.

The end of the polyvinyl ether compound having the structural unit represented by the general formula (1) can be converted into a desired structure by a method described in the present disclosure and a publicly known method. Examples of the group introduced by conversion include saturated hydrocarbons, ethers, alcohols, ketones, amides, and nitriles.

The polyvinyl ether compound preferably has the following end structures.

(In the formula, R¹¹, R²¹, and R³¹ may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R⁴¹ represents a divalent hydrocarbon group having 1 to 10 carbon atoms or an ether bond oxygen-containing divalent hydrocarbon group having 2 to 20 carbon atoms, R⁵¹ represents a hydrocarbon group having 1 to 20 carbon atoms, m represents a number at which the average of m in the polyvinyl ether is 0 to 10, and when m represents 2 or more, a plurality of R⁴¹O may be the same or different.)

(In the formula, R⁶¹, R⁷¹, R⁸¹, and R⁹¹ may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)

(In the formula, R¹², R²², and R³² may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R⁴² represents a divalent hydrocarbon group having 1 to 10 carbon atoms or an ether bond oxygen-containing divalent hydrocarbon group having 2 to 20 carbon atoms, R⁵² represents a hydrocarbon group having 1 to 20 carbon atoms, m represents a number at which the average of m in the polyvinyl ether is 0 to 10, and when m represents 2 or more, a plurality of R⁴²O may be the same or different.)

(In the formula, R⁶², R⁷², R⁸², and R⁹² may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)

(In the formula, R¹³, R²³, and R³³ may be the same or different and each represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.)

The polyvinyl ether oil according to this embodiment can be produced by polymerizing the above-described monomer through, for example, radical polymerization, cationic polymerization, or radiation-induced polymerization. After completion of the polymerization reaction, a typical separation/purification method is performed when necessary to obtain a desired polyvinyl ether compound having a structural unit represented by the general formula (1).

(Polyoxyalkylene Oil)

The polyoxyalkylene oil is a polyoxyalkylene compound obtained by, for example, polymerizing an alkylene oxide having 2 to 4 carbon atoms (e.g., ethylene oxide or propylene oxide) using water or a hydroxyl group-containing compound as an initiator. The hydroxyl group of the polyoxyalkylene compound may be etherified or esterified. The polyoxyalkylene oil may contain an oxyalkylene unit of the same type or two or more oxyalkylene units in one molecule. The polyoxyalkylene oil preferably contains at least an oxypropylene unit in one molecule.

Specifically, the polyoxyalkylene oil is, for example, a compound represented by general formula (9) below.

R¹⁰¹—[(OR¹⁰²)_(k)—OR¹⁰³]_(l)  (9)

(In the formula, R¹⁰¹ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 2 to 10 carbon atoms, or an aliphatic hydrocarbon group having 2 to 6 bonding sites and 1 to 10 carbon atoms, R¹⁰² represents an alkylene group having 2 to 4 carbon atoms, R¹⁰³ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group having 2 to 10 carbon atoms, l represents an integer of 1 to 6, and k represents a number at which the average of k×l is 6 to 80.)

In the general formula (9), the alkyl group represented by R¹⁰¹ and R¹⁰³ may be a linear, branched, or cyclic alkyl group. Specific examples of the alkyl group include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, a cyclopentyl group, and a cyclohexyl group. If the number of carbon atoms of the alkyl group exceeds 10, the miscibility with a refrigerant deteriorates, which may cause phase separation. The number of carbon atoms of the alkyl group is preferably 1 to 6.

The acyl group represented by R¹⁰¹ and R¹⁰³ may have a linear, branched, or cyclic alkyl group moiety. Specific examples of the alkyl group moiety of the acyl group include various groups having 1 to 9 carbon atoms that are mentioned as specific examples of the alkyl group. If the number of carbon atoms of the acyl group exceeds 10, the miscibility with a refrigerant deteriorates, which may cause phase separation. The number of carbon atoms of the acyl group is preferably 2 to 6.

When R¹⁰¹ and R¹⁰³ each represent an alkyl group or an acyl group, R¹⁰¹ and R¹⁰³ may be the same or different.

Furthermore, when l represents 2 or more, a plurality of R¹⁰³ in one molecule may be the same or different.

When R¹⁰¹ represents an aliphatic hydrocarbon group having 2 to 6 bonding sites and 1 to 10 carbon atoms, the aliphatic hydrocarbon group may be a linear group or a cyclic group. Examples of the aliphatic hydrocarbon group having two bonding sites include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a cyclopentylene group, and a cyclohexylene group. Examples of the aliphatic hydrocarbon group having 3 to 6 bonding sites include residual groups obtained by removing hydroxyl groups from polyhydric alcohols such as trimethylolpropane, glycerol, pentaerythritol, sorbitol, 1,2,3-trihydroxycyclohexane, and 1,3,5-trihydroxycyclohexane.

If the number of carbon atoms of the aliphatic hydrocarbon group exceeds 10, the miscibility with a refrigerant deteriorates, which may cause phase separation. The number of carbon atoms is preferably 2 to 6.

R¹⁰² in the general formula (9) represents an alkylene group having 2 to 4 carbon atoms. Examples of the oxyalkylene group serving as a repeating unit include an oxyethylene group, an oxypropylene group, and an oxybutylene group. The polyoxyalkylene oil may contain an oxyalkylene group of the same type or two or more oxyalkylene groups in one molecule, but preferably contains at least an oxypropylene unit in one molecule. In particular, the content of the oxypropylene unit in the oxyalkylene unit is suitably 50 mol % or more.

In the general formula (9), l represents an integer of 1 to 6, which can be determined in accordance with the number of bonding sites of R¹⁰¹. For example, when R¹⁰¹ represents an alkyl group or an acyl group, l represents 1. When R¹⁰¹ represents an aliphatic hydrocarbon group having 2, 3, 4, 5, and 6 bonding sites, l represents 2, 3, 4, 5, and 6, respectively. Preferably, l represents 1 or 2. Furthermore, k preferably represents a number at which the average of k×l is 6 to 80.

For the structure of the polyoxyalkylene oil, a polyoxypropylene diol dimethyl ether represented by general formula (10) below and a poly(oxyethylene/oxypropylene) diol dimethyl ether represented by general formula (11) below are suitable from the viewpoints of economy and the above-described effects. Furthermore, a polyoxypropylene diol monobutyl ether represented by general formula (12) below, a polyoxypropylene diol monomethyl ether represented by general formula (13) below, a poly(oxyethylene/oxypropylene) diol monomethyl ether represented by general formula (14) below, a poly(oxyethylene/oxypropylene) diol monobutyl ether represented by general formula (15) below, and a polyoxypropylene diol diacetate represented by general formula (16) below are suitable from the viewpoint of economy and the like.

CH₃O—(C₃H₆O)_(h)—CH₃  (10)

(in the formula, h represents 6 to 80.)

CH₃O—(C₂H₄O)_(i)—(C₃H₆O)_(j)—CH₃  (1)

(In the formula, i and j each represent 1 or more and the sum of i and j is 6 to 80.)

C₄H₉O—(C₃H₆O)_(h)—H  (12)

(In the formula, h represents 6 to 80.)

CH₃O—(C₃H₆O)_(h)—H  (13)

(In the formula, h represents 6 to 80.)

CH₃O—(C₂H₄O)_(i)—(C₃H₆O)_(j)—H  (14)

(In the formula, i and j each represent 1 or more and the sum of i and j is 6 to 80.)

C₄H₉O—(C₂H₄O)_(i)—(C₃H₆O)_(j)—H  (15)

(In the formula, i and j each represent 1 or more and the sum of i and j is 6 to 80.)

CH₃COO—(C₃H₆O)_(h)—COCH₃  (16)

(In the formula, h represents 6 to 80.)

The polyoxyalkylene oils may be used alone or in combination of two or more.

(2-2) Hydrocarbon Refrigerating Oil

The hydrocarbon refrigerating oil that can be used is, for example, an alkylbenzene.

The alkylbenzene that can be used is a branched alkylbenzene synthesized from propylene polymer and benzene serving as raw materials using a catalyst such as hydrogen fluoride or a linear alkylbenzene synthesized from normal paraffin and benzene serving as raw materials using the same catalyst. The number of carbon atoms of the alkyl group is preferably 1 to 30 and more preferably 4 to 20 from the viewpoint of achieving a viscosity appropriate as a lubricating base oil. The number of alkyl groups in one molecule of the alkylbenzene is dependent on the number of carbon atoms of the alkyl group, but is preferably 1 to 4 and more preferably 1 to 3 to control the viscosity within the predetermined range.

The hydrocarbon refrigerating oil preferably circulates through a refrigeration cycle system together with a refrigerant. Although it is most preferable that the refrigerating oil is soluble with a refrigerant, for example, a refrigerating oil (e.g., a refrigerating oil disclosed in Japanese Patent No. 2803451) having low solubility can also be used as long as the refrigerating oil is capable of circulating through a refrigeration cycle system together with a refrigerant. To allow the refrigerating oil to circulate through a refrigeration cycle system, the refrigerating oil is required to have a low kinematic viscosity. The kinematic viscosity of the hydrocarbon refrigerating oil at 40° C. is preferably 1 mm²/s or more and 50 mm²/s or less and more preferably 1 mm²/s or more and 25 mm²/s or less.

These refrigerating oils may be used alone or in combination of two or more.

The content of the hydrocarbon refrigerating oil in the working fluid for a refrigerating machine may be, for example, 10 parts by mass or more and 100 parts by mass or less and is more preferably 20 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the refrigerant composition.

(2-3) Additive

The refrigerating oil may contain one or two or more additives.

Examples of the additives include an acid scavenger, an extreme pressure agent, an antioxidant, an antifoaming agent, an oiliness improver, a metal deactivator such as a copper deactivator, an anti-wear agent, and a compatibilizer.

Examples of the acid scavenger that can be used include epoxy compounds such as phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxide, and epoxidized soybean oil; and carbodiimides. Among them, phenyl glycidyl ether, alkyl glycidyl ether, alkylene glycol glycidyl ether, cyclohexene oxide, and α-olefin oxide are preferred from the viewpoint of miscibility. The alkyl group of the alkyl glycidyl ether and the alkylene group of the alkylene glycol glycidyl ether may have a branched structure. The number of carbon atoms may be 3 or more and 30 or less, and is more preferably 4 or more and 24 or less and further preferably 6 or more and 16 or less. The total number of carbon atoms of the α-olefin oxide may be 4 or more and 50 or less, and is more preferably 4 or more and 24 or less and further preferably 6 or more and 16 or less. The acid scavengers may be used alone or in combination of two or more.

The extreme pressure agent may contain, for example, a phosphoric acid ester. Examples of the phosphoric acid ester that can be used include phosphoric acid esters, phosphorous acid esters, acidic phosphoric acid esters, and acidic phosphorous acid esters. The extreme pressure agent may contain an amine salt of a phosphoric acid ester, a phosphorous acid ester, an acidic phosphoric acid ester, or an acidic phosphorous acid ester.

Examples of the phosphoric acid ester include triaryl phosphates, trialkyl phosphates, trialkylaryl phosphates, triarylalkyl phosphates, and trialkenyl phosphates. Specific examples of the phosphoric acid ester include triphenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, ethyl diphenyl phosphate, tributyl phosphate, ethyl dibutyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, ethylphenyl diphenyl phosphate, diethylphenyl phenyl phosphate, propylphenyl diphenyl phosphate, dipropylphenyl phenyl phosphate, triethylphenyl phosphate, tripropylphenyl phosphate, butylphenyl diphenyl phosphate, dibutylphenyl phenyl phosphate, tributylphenyl phosphate, trihexyl phosphate, tri(2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, and trioleyl phosphate.

Specific examples of the phosphorous acid ester include triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tri(nonylphenyl) phosphite, tri(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, and trioleyl phosphite.

Specific examples of the acidic phosphoric acid ester include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate, and isostearyl acid phosphate.

Specific examples of the acidic phosphorous acid ester include dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, and diphenyl hydrogen phosphite. Among the phosphoric acid esters, oleyl acid phosphate and stearyl acid phosphate are suitably used.

Among amines used for amine salts of phosphoric acid esters, phosphorous acid esters, acidic phosphoric acid esters, or acidic phosphorous acid esters, specific examples of mono-substituted amines include butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, laurylamine, stearylamine, oleylamine, and benzylamine. Specific examples of di-substituted amines include dibutylamine, dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, dibenzylamine, stearyl-monoethanolamine, decyl-monoethanolamine, hexyl-monopropanolamine, benzyl-monoethanolamine, phenyl-monoethanolamine, and tolyl-monopropanolamine. Specific examples of tri-substituted amines include tributylamine, tripentylamine, trihexylamine, tricyclohexylamine, trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl-monoethanolamine, dilauryl-monopropanolamine, dioctyl-monoethanolamine, dihexyl-monopropanolamine, dibutyl-monopropanolamine, oleyl-diethanolamine, stearyl-dipropanolamine, lauryl-diethanolamine, octyl-dipropanolamine, butyl-diethanolamine, benzyl-diethanolamine, phenyl-diethanolamine, tolyl-dipropanolamine, xylyl-diethanolamine, triethanolamine, and tripropanolamine.

Examples of extreme pressure agents other than the above-described extreme pressure agents include extreme pressure agents based on organosulfur compounds such as monosulfides, polysulfides, sulfoxides, sulfones, thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes, thiazoles, and methanesulfonates; extreme pressure agents based on thiophosphoric acid esters such as thiophosphoric acid triesters; extreme pressure agents based on esters such as higher fatty acids, hydroxyaryl fatty acids, polyhydric alcohol esters, and acrylic acid esters; extreme pressure agents based on organochlorine compounds such as chlorinated hydrocarbons, e.g., chlorinated paraffin and chlorinated carboxylic acid derivatives; extreme pressure agents based on fluoroorganic compounds such as fluorinated aliphatic carboxylic acids, fluorinated ethylene resins, fluorinated alkylpolysiloxanes, and fluorinated graphites; extreme pressure agents based on alcohols such as higher alcohols; and extreme pressure agents based on metal compounds such as naphthenic acid salts (e.g., lead naphthenate), fatty acid salts (e.g., lead fatty acid), thiophosphoric acid salts (e.g., zinc dialkyldithiophosphate), thiocarbamic acid salts, organomolybdenum compounds, organotin compounds, organogermanium compounds, and boric acid esters.

The antioxidant that can be used is, for example, a phenol-based antioxidant or an amine-based antioxidant. Examples of the phenol-based antioxidant include 2,6-di-tert-butyl-4-methylphenol (DBPC), 2,6-di-tert-butyl-4-ethylphenol, 2,2′-methylenebis(4-methyl-6-tert-butylphenol), 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butylphenol, di-tert-butyl-p-cresol, and bisphenol A. Examples of the amine-based antioxidant include N,N′-diisopropyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, phenyl-α-naphthylamine, N,N′-di-phenyl-p-phenylenediamine, and N,N-di(2-naphthyl)-p-phenylenediamine. An oxygen scavenger that captures oxygen can also be used as the antioxidant.

The antifoaming agent that can be used is, for example, a silicon compound.

The oiliness improver that can be used is, for example, a higher alcohol or a fatty acid.

The metal deactivator such as a copper deactivator that can be used is, for example, benzotriazole or a derivative thereof.

The anti-wear agent that can be used is, for example, zinc dithiophosphate.

The compatibilizer is not limited, and can be appropriately selected from commonly used compatibilizers. The compatibilizers may be used alone or in combination of two or more. Examples of the compatibilizer include polyoxyalkylene glycol ethers, amides, nitriles, ketones, chlorocarbons, esters, lactones, aryl ethers, fluoroethers, and 1,1,1-trifluoroalkanes. The compatibilizer is particularly preferably a polyoxyalkylene glycol ether.

The refrigerating oil may optionally contain, for example, a load-bearing additive, a chlorine scavenger, a detergent dispersant, a viscosity index improver, a heat resistance improver, a stabilizer, a corrosion inhibitor, a pour-point depressant, and an anticorrosive.

The content of each additive in the refrigerating oil may be 0.01 mass % or more and 5 mass % or less and is preferably 0.05 mass % or more and 3 mass % or less. The content of the additive in the working fluid for a refrigerating machine constituted by the refrigerant composition and the refrigerating oil is preferably 5 mass % or less and more preferably 3 mass % or less.

The refrigerating oil preferably has a chlorine concentration of 50 ppm or less and preferably has a sulfur concentration of 50 ppm or less.

(3) Embodiment of the Technique of Third Group

A refrigeration apparatus of the technique of first group and third group is an air conditioning apparatus.

(3-1) First Embodiment

An air conditioning apparatus 1 serving as a refrigeration cycle apparatus according to a first embodiment is described below with reference to FIG. 3A which is a schematic configuration diagram of a refrigerant circuit and FIG. 3B which is a schematic control block configuration diagram.

The air conditioning apparatus 1 is an apparatus that controls the condition of air in a subject space by performing a vapor compression refrigeration cycle.

The air conditioning apparatus 1 mainly includes an outdoor unit 20, an indoor unit 30, a liquid-side connection pipe 6 and a gas-side connection pipe 5 that connect the outdoor unit 20 and the indoor unit 30 to each other, a remote controller (not illustrated) serving as an input device and an output device, and a controller 7 that controls operations of the air conditioning apparatus 1.

The air conditioning apparatus 1 performs a refrigeration cycle in which a refrigerant enclosed in a refrigerant circuit 10 is compressed, cooled or condensed, decompressed, heated or evaporated, and then compressed again. In the present embodiment, the refrigerant circuit 10 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and can use any one of the above-described refrigerants A to D. Moreover, the refrigerant circuit 10 is filled with a refrigerator oil together with the mixed refrigerant.

(3-1-1) Outdoor Unit 20

The outdoor unit 20 is connected to the indoor unit 30 via the liquid-side connection pipe 6 and the gas-side connection pipe 5, and constitutes a part of the refrigerant circuit 10. The outdoor unit 20 mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, an outdoor expansion valve 24, an outdoor fan 25, a liquid-side shutoff valve 29, and a gas-side shutoff valve 28.

The compressor 21 is a device that compresses the refrigerant with a low pressure in the refrigeration cycle until the refrigerant becomes a high-pressure refrigerant. In this case, a compressor having a hermetically sealed structure in which a compression element (not illustrated) of positive-displacement type, such as rotary type or scroll type, is rotationally driven by a compressor motor is used as the compressor 21. The compressor motor is for changing the capacity, and has an operational frequency that can be controlled by an inverter. The compressor 21 is provided with an additional accumulator (not illustrated) on the suction side (note that the inner capacity of the additional accumulator is smaller than each of the inner capacities of a low-pressure receiver, an intermediate-pressure receiver, and a high-pressure receiver which are described later, and is preferably less than or equal to a half of each of the inner capacities).

The four-way switching valve 22, by switching the connection state, can switch the state between a cooling operation connection state in which the discharge side of the compressor 21 is connected to the outdoor heat exchanger 23 and the suction side of the compressor 21 is connected to the gas-side shutoff valve 28, and a heating operation connection state in which the discharge side of the compressor 21 is connected to the gas-side shutoff valve 28 and the suction side of the compressor 21 is connected to the outdoor heat exchanger 23.

The outdoor heat exchanger 23 is a heat exchanger that functions as a condenser for the high-pressure refrigerant in the refrigeration cycle during cooling operation and that functions as an evaporator for the low-pressure refrigerant in the refrigeration cycle during heating operation.

The outdoor fan 25 sucks outdoor air into the outdoor unit 20, causes the outdoor air to exchange heat with the refrigerant in the outdoor heat exchanger 23, and then generates an air flow to be discharged to the outside. The outdoor fan 25 is rotationally driven by an outdoor fan motor.

The outdoor expansion valve 24 is provided between a liquid-side end portion of the outdoor heat exchanger 23 and the liquid-side shutoff valve 29. The outdoor expansion valve 24 may be, for example, a capillary tube or a mechanical expansion valve that is used together with a temperature-sensitive tube. Preferably, the outdoor expansion valve 24 is an electric expansion valve that can control the valve opening degree through control.

The liquid-side shutoff valve 29 is a manual valve disposed in a connection portion of the outdoor unit 20 with respect to the liquid-side connection pipe 6.

The gas-side shutoff valve 28 is a manual valve disposed in a connection portion of the outdoor unit 20 with respect to the gas-side connection pipe 5.

The outdoor unit 20 includes an outdoor-unit control unit 27 that controls operations of respective sections constituting the outdoor unit 20. The outdoor-unit control unit 27 includes a microcomputer including a CPU, a memory, and so forth. The outdoor-unit control unit 27 is connected to an indoor-unit control unit 34 of each indoor unit 30 via a communication line, and transmits and receives a control signal and so forth.

The outdoor unit 20 includes, for example, a discharge pressure sensor 61, a discharge temperature sensor 62, a suction pressure sensor 63, a suction temperature sensor 64, an outdoor heat-exchange temperature sensor 65, and an outdoor air temperature sensor 66. Each of the sensors is electrically connected to the outdoor-unit control unit 27, and transmits a detection signal to the outdoor-unit control unit 27. The discharge pressure sensor 61 detects the pressure of the refrigerant flowing through a discharge pipe that connects the discharge side of the compressor 21 to one of connecting ports of the four-way switching valve 22. The discharge temperature sensor 62 detects the temperature of the refrigerant flowing through the discharge pipe. The suction pressure sensor 63 detects the pressure of the refrigerant flowing through a suction pipe that connects the suction side of the compressor 21 to one of the connecting ports of the four-way switching valve 22. The suction temperature sensor 64 detects the temperature of the refrigerant flowing through the suction pipe. The outdoor heat-exchange temperature sensor 65 detects the temperature of the refrigerant flowing through the outlet on the liquid side of the outdoor heat exchanger 23 opposite to the side connected to the four-way switching valve 22. The outdoor air temperature sensor 66 detects the outdoor air temperature before passing through the outdoor heat exchanger 23.

(3-1-2) Indoor Unit 30

The indoor unit 30 is installed on a wall surface or a ceiling in a room that is a subject space. The indoor unit 30 is connected to the outdoor unit 20 via the liquid-side connection pipe 6 and the gas-side connection pipe 5, and constitutes a part of the refrigerant circuit 10.

The indoor unit 30 includes an indoor heat exchanger 31 and an indoor fan 32.

The liquid side of the indoor heat exchanger 31 is connected to the liquid-side connection pipe 6, and the gas-side end thereof is connected to the gas-side connection pipe 5. The indoor heat exchanger 31 is a heat exchanger that functions as an evaporator for the low-pressure refrigerant in the refrigeration cycle during cooling operation and that functions as a condenser for the high-pressure refrigerant in the refrigeration cycle during heating operation.

The indoor fan 32 sucks indoor air into the indoor unit 30, causes the indoor air to exchange heat with the refrigerant in the indoor heat exchanger 31, and then generates an air flow to be discharged to the outside. The indoor fan 32 is rotationally driven by an indoor fan motor.

The indoor unit 30 includes an indoor-unit control unit 34 that controls operations of respective sections constituting the indoor unit 30. The indoor-unit control unit 34 includes a microcomputer including a CPU, a memory, and so forth. The indoor-unit control unit 34 is connected to the outdoor-unit control unit 27 via a communication line, and transmits and receives a control signal and so forth.

The indoor unit 30 includes, for example, an indoor liquid-side heat-exchange temperature sensor 71 and an indoor air temperature sensor 72. Each of the sensors is electrically connected to the indoor-unit control unit 34, and transmits a detection signal to the indoor-unit control unit 34. The indoor liquid-side heat-exchange temperature sensor 71 detects the temperature of the refrigerant flowing through the outlet on the liquid side of the indoor heat exchanger 31 opposite to the side connected to the four-way switching valve 22. The indoor air temperature sensor 72 detects the indoor air temperature before passing through the indoor heat exchanger 31.

(3-1-3) Details of Controller 7

In the air conditioning apparatus 1, the outdoor-unit control unit 27 is connected to the indoor-unit control unit 34 via the communication line, thereby constituting the controller 7 that controls operations of the air conditioning apparatus 1.

The controller 7 mainly includes a CPU (central processing unit) and a memory, such as a ROM or a RAM. Various processing and control by the controller 7 are provided when respective sections included in the outdoor-unit control unit 27 and/or the indoor-unit control unit 34 function together.

(3-1-4) Operating Modes

Operating modes are described below.

The operating modes include a cooling operating mode and a heating operating mode.

The controller 7 determines whether the operating mode is the cooling operating mode or the heating operating mode and executes the determined mode based on an instruction received from the remote controller or the like.

(3-1-4-1) Cooling Operating Mode

In the air conditioning apparatus 1, in the cooling operating mode, the connection state of the four-way switching valve 22 is in the cooling operation connection state in which the discharge side of the compressor 21 is connected to the outdoor heat exchanger 23 and the suction side of the compressor 21 is connected to the gas-side shutoff valve 28, and the refrigerant filled in the refrigerant circuit 10 is circulated mainly sequentially in the compressor 21, the outdoor heat exchanger 23, the outdoor expansion valve 24, and the indoor heat exchanger 31.

More specifically, in the refrigerant circuit 10, when the cooling operating mode is started, the refrigerant is sucked into the compressor 21, compressed, and then discharged.

The compressor 21 performs capacity control in accordance with a cooling load required for the indoor unit 30. The capacity control is not limited, and, for example, controls the operating frequency of the compressor 21 such that, when the air conditioning apparatus 1 is controlled to cause the indoor air temperature to attain a set temperature, the discharge temperature (the detected temperature of the discharge temperature sensor 62) becomes a value corresponding to the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and flows into the gas-side end of the outdoor heat exchanger 23.

The gas refrigerant which has flowed into the gas-side end of the outdoor heat exchanger 23 exchanges heat with outdoor-side air supplied by the outdoor fan 25, hence is condensed and turns into a liquid refrigerant in the outdoor heat exchanger 23, and flows out from the liquid-side end of the outdoor heat exchanger 23.

The refrigerant which has flowed out from the liquid-side end of the outdoor heat exchanger 23 is decompressed when passing through the outdoor expansion valve 24. The outdoor expansion valve 24 is controlled, for example, such that the degree of superheating of the refrigerant to be sucked into the compressor 21 becomes a target value of a predetermined degree of superheating. In this case, the degree of superheating of the sucked refrigerant of the compressor 21 can be obtained, for example, by subtracting a saturation temperature corresponding to a suction pressure (the detected pressure of the suction pressure sensor 63) from a suction temperature (the detected temperature of the suction temperature sensor 64). Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and flows into the indoor unit 30.

The refrigerant which has flowed into the indoor unit 30 flows into the indoor heat exchanger 31; exchanges heat with the indoor air supplied by the indoor fan 32, hence is evaporated, and turns into a gas refrigerant in the indoor heat exchanger 30; and flows out from the gas-side end of the indoor heat exchanger 31. The gas refrigerant which has flowed out from the gas-side end of the indoor heat exchanger 31 flows to the gas-side connection pipe 5.

The refrigerant which has flowed through the gas-side connection pipe 5 passes through the gas-side shutoff valve 28 and the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-1-4-2) Heating Operating Mode

In the air conditioning apparatus 1, in the heating operating mode, the connection state of the four-way switching valve 22 is in the heating operation connection state in which the discharge side of the compressor 21 is connected to the gas-side shutoff valve 28 and the suction side of the compressor 21 is connected to the outdoor heat exchanger 23, and the refrigerant filled in the refrigerant circuit 10 is circulated mainly sequentially in the compressor 21, the indoor heat exchanger 31, the outdoor expansion valve 24, and the outdoor heat exchanger 23.

More specifically, in the refrigerant circuit 10, when the heating operating mode is started, the refrigerant is sucked into the compressor 21, compressed, and then discharged.

The compressor 21 performs capacity control in accordance with a heating load required for the indoor unit 30. The capacity control is not limited, and, for example, controls the operating frequency of the compressor 21 such that, when the air conditioning apparatus 1 is controlled to cause the indoor air temperature to attain a set temperature, the discharge temperature (the detected temperature of the discharge temperature sensor 62) becomes a value corresponding to the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, and then flows into the indoor unit 30.

The refrigerant which has flowed into the indoor unit 30 flows into the gas-side end of the indoor heat exchanger 31; exchanges heat with the indoor air supplied by the indoor fan 32, hence is condensed, and turns into a refrigerant in a gas-liquid two-phase state or a liquid refrigerant in the indoor heat exchanger 31; and flows out from the liquid-side end of the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows to the liquid-side connection pipe 6.

The refrigerant which has flowed through the liquid-side connection pipe 6 flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, and is decompressed to a low pressure in the refrigeration cycle at the outdoor expansion valve 24. The outdoor expansion valve 24 is controlled, for example, such that the degree of superheating of the refrigerant to be sucked into the compressor 21 becomes a target value of a predetermined degree of superheating. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 flows into the liquid-side end of the outdoor heat exchanger 23.

The refrigerant which has flowed in from the liquid-side end of the outdoor heat exchanger 23 exchanges heat with the outdoor air supplied by the outdoor fan 25, hence is evaporated and turns into a gas refrigerant in the outdoor heat exchanger 23, and flows out from the gas-side end of the outdoor heat exchanger 23.

The refrigerant which has flowed out from the gas-side end of the outdoor heat exchanger 23 passes through the four-way switching valve 22 and is sucked into the compressor 21 again.

(3-1-5) Characteristics of First Embodiment

Since the air conditioning apparatus 1 can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 can perform a refrigeration cycle using a small-GWP refrigerant.

(3-2) Second Embodiment

An air conditioning apparatus 1 a serving as a refrigeration cycle apparatus according to a second embodiment is described below with reference to FIG. 3C which is a schematic configuration diagram of a refrigerant circuit and FIG. 3D which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 according to the first embodiment are mainly described below.

(3-2-1) Schematic Configuration of Air Conditioning Apparatus 1 a

The air conditioning apparatus 1 a differs from the air conditioning apparatus 1 according to the first embodiment in that the outdoor unit 20 includes a low-pressure receiver 41.

The low-pressure receiver 41 is a refrigerant container that is provided between the suction side of the compressor 21 and one of the connecting ports of the four-way switching valve 22 and that can store an excessive refrigerant in the refrigerant circuit 10 as a liquid refrigerant. Note that, in the present embodiment, the suction pressure sensor 63 and the suction temperature sensor 64 are provided to detect, as a subject, the refrigerant flowing between the low-pressure receiver 41 and the suction side of the compressor 21. Moreover, the compressor 21 is provided with an additional accumulator (not illustrated). The low-pressure receiver 41 is connected to the downstream side of the additional accumulator.

(3-2-2) Cooling Operating Mode

In the air conditioning apparatus 1 a, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72). The evaporation temperature is not limited; however, may be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22, the outdoor heat exchanger 23, and the outdoor expansion valve 24 in that order.

In this case, the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the outdoor heat exchanger 23 becomes a target value. The degree of subcooling of the refrigerant flowing through the liquid-side outlet of the outdoor heat exchanger 23 is not limited; however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to a high pressure of the refrigerant circuit 10 (the detected pressure of the discharge pressure sensor 61) from the detected temperature of the outdoor heat-exchange temperature sensor 65. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, flows into the indoor unit 30, is evaporated in the indoor heat exchanger 31, and flows into the gas-side connection pipe 5. The refrigerant which has flowed through the gas-side connection pipe 5 passes through the gas-side shutoff valve 28, the four-way switching valve 22, and the low-pressure receiver 41, and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerant which has not been completely evaporated in the indoor heat exchanger 31.

(3-2-3) Heating Operating Mode

In the air conditioning apparatus 1 a, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72). The condensation temperature is not limited; however, may be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, then flows into the gas-side end of the indoor heat exchanger 31 of the indoor unit 30, and is condensed in the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows through the liquid-side connection pipe 6, flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, and is decompressed to a low pressure in the refrigeration cycle at the outdoor expansion valve 24. Note that the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the indoor heat exchanger 31 becomes a target value. The degree of subcooling of the refrigerant flowing through the liquid-side outlet of the indoor heat exchanger 31 is not limited; however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to a high pressure of the refrigerant circuit 10 (the detected pressure of the discharge pressure sensor 61) from the detected temperature of the indoor liquid-side heat-exchange temperature sensor 71. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22 and the low-pressure receiver 41, and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerant which has not been completely evaporated in the outdoor heat exchanger 23.

(3-2-4) Characteristics of Second Embodiment

Since the air conditioning apparatus 1 a can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 a can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 a is provided with the low-pressure receiver 41, occurrence of liquid compression is prevented without execution of control (control of the outdoor expansion valve 24) to ensure that the degree of superheating of the refrigerant to be sucked into the compressor 21 is a predetermined value or more. Owing to this, the control of the outdoor expansion valve 24 can be control to sufficiently ensure the degree of subcooling of the refrigerant flowing through the outlet for the outdoor heat exchanger 23 when functioning as the condenser (which is similarly applied to the indoor heat exchanger 31 when functioning as the condenser).

(3-3) Third Embodiment

An air conditioning apparatus 1 b serving as a refrigeration cycle apparatus according to a third embodiment is described below with reference to FIG. 3E which is a schematic configuration diagram of a refrigerant circuit and FIG. 3F which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 a according to the second embodiment are mainly described below.

(3-3-1) Schematic Configuration of Air Conditioning Apparatus 1 b

The air conditioning apparatus 1 b differs from the air conditioning apparatus 1 a according to the second embodiment in that a plurality of indoor units are provided in parallel and an indoor expansion valve is provided on the liquid-refrigerant side of an indoor heat exchanger in each indoor unit.

The air conditioning apparatus 1 b includes a first indoor unit 30 and a second indoor unit 35 connected in parallel to each other. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor heat exchanger 31 and a first indoor fan 32, and a first indoor expansion valve 33 is provided on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor expansion valve 33 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor-unit control unit 34; and a first indoor liquid-side heat-exchange temperature sensor 71, a first indoor air temperature sensor 72, and a first indoor gas-side heat-exchange temperature sensor 73 that are electrically connected to the first indoor-unit control unit 34. The first indoor liquid-side heat-exchange temperature sensor 71 detects the temperature of the refrigerant flowing through the outlet on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor gas-side heat-exchange temperature sensor 73 detects the temperature of the refrigerant flowing through the outlet on the gas-refrigerant side of the first indoor heat exchanger 31. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor heat exchanger 36 and a second indoor fan 37, and a second indoor expansion valve 38 is provided on the liquid-refrigerant side of the second indoor heat exchanger 36. The second indoor expansion valve 38 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor-unit control unit 39, and a second indoor liquid-side heat-exchange temperature sensor 75, a second indoor air temperature sensor 76, and a second indoor gas-side heat-exchange temperature sensor 77 that are electrically connected to the second indoor-unit control unit 39.

The air conditioning apparatus 1 b differs from the air conditioning apparatus 1 a according to the second embodiment in that, in an outdoor unit, the outdoor expansion valve 24 is not provided and a bypass pipe 40 having a bypass expansion valve 49 is provided.

The bypass pipe 40 is a refrigerant pipe that connects a refrigerant pipe extending from the outlet on the liquid-refrigerant side of the outdoor heat exchanger 23 to the liquid-side shutoff valve 29 and a refrigerant pipe extending from one of the connecting ports of the four-way switching valve 22 to the low-pressure receiver 41 to each other. The bypass expansion valve 49 is preferably an electric expansion valve of which the valve opening degree is adjustable. The bypass pipe 40 is not limited to one provided with the electric expansion valve of which the opening degree is adjustable, and may be, for example, one having a capillary tube and an openable and closable electromagnetic valve.

(3-3-2) Cooling Operating Mode

In the air conditioning apparatus 1 b, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load). The evaporation temperature is not limited; however, can be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63.

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and is sent to the first indoor unit 30 and the second indoor unit 35.

In this case, in the first indoor unit 30, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the first indoor heat exchanger 31 becomes a target value. The degree of superheating of the refrigerant flowing through the gas-side outlet of the first indoor heat exchanger 31 is not limited; however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to a low pressure of the refrigerant circuit 10 (the detected pressure of the suction pressure sensor 63) from the detected temperature of the first indoor gas-side heat-exchange temperature sensor 73. Moreover, also for the second indoor expansion valve 38 of the second indoor unit 35, similarly to the first indoor expansion valve 33, the valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the second indoor heat exchanger 36 becomes a target value. The degree of superheating of the refrigerant flowing through the gas-side outlet of the second indoor heat exchanger 36 is not limited, however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to a low pressure of the refrigerant circuit 10 (the detected pressure of the suction pressure sensor 63) from the detected temperature of the second indoor gas-side heat-exchange temperature sensor 77. Each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 may be controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Furthermore, the method of controlling each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first indoor expansion valve 33 is evaporated in the first indoor heat exchanger 31, the refrigerant decompressed at the second indoor expansion valve 38 is evaporated in the second indoor heat exchanger 36, and the evaporated refrigerants are joined. Then, the joined refrigerant flows to the gas-side connection pipe 5. The refrigerant which has flowed through the gas-side connection pipe 5 passes through the gas-side shutoff valve 28, the four-way switching valve 22, and the low-pressure receiver 41, and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerants which have not been completely evaporated in the first indoor heat exchanger 31 and the second indoor heat exchanger 36. Note that the bypass expansion valve 49 of the bypass pipe 40 is controlled to be opened or controlled such that the valve opening degree thereof is increased when the predetermined condition relating to that the refrigerant amount in the outdoor heat exchanger 23 serving as the condenser is excessive. The control on the opening degree of the bypass expansion valve 49 is not limited; however, for example, when the condensation pressure (for example, the detected pressure of the discharge pressure sensor 61) is a predetermined value or more, the control may be of opening the bypass expansion valve 49 or increasing the opening degree of the bypass expansion valve 49. Alternatively, the control may be of switching the bypass expansion valve 49 between an open state and a closed state at a predetermined time interval to increase the passing flow rate.

(3-3-3) Heating Operating Mode

In the air conditioning apparatus 1 b, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load). The condensation temperature is not limited; however, may be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5; then a portion of the refrigerant flows into the gas-side end of the first indoor heat exchanger 31 of the first indoor unit 30 and is condensed in the first indoor heat exchanger 31; and another portion of the refrigerant flows into the gas-side end of the second indoor heat exchanger 36 of the second indoor unit 35 and is condensed in the second indoor heat exchanger 36.

Note that, the valve opening degree of the first indoor expansion valve 33 of the first indoor unit 30 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid side of the first indoor heat exchanger 31 becomes a predetermined target value. Also for the second indoor expansion valve 38 of the second indoor unit 35, the valve opening degree of the second indoor expansion valve 38 is controlled likewise to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid side of the second indoor heat exchanger 36 becomes a predetermined target value. The degree of subcooling of the refrigerant flowing through the liquid side of the first indoor heat exchanger 31 can be obtained by subtracting the saturation temperature of the refrigerant corresponding to a high pressure of the refrigerant circuit 10 (the detected pressure of the discharge pressure sensor 61) from the detected temperature of the first indoor liquid-side heat-exchange temperature sensor 71. Also, the degree of subcooling of the refrigerant flowing through the liquid side of the second indoor heat exchanger 36 may be similarly obtained by subtracting the saturation temperature of the refrigerant corresponding to a high pressure of the refrigerant circuit 10 (the detected pressure of the discharge pressure sensor 61) from the detected temperature of the second indoor liquid-side heat-exchange temperature sensor 75.

The refrigerant decompressed at the first indoor expansion valve 33 and the refrigerant decompressed at the second indoor expansion valve 38 are joined. The joined refrigerant passes through the liquid-side connection pipe 6 and the liquid-side shutoff valve 29, then is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22 and the low-pressure receiver 41, and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerant which has not been completely evaporated in the outdoor heat exchanger 23. In heating operation, although not limited, the bypass expansion valve 49 of the bypass pipe 40 may be maintained in, for example, a full-close state.

(3-3-4) Characteristics of Third Embodiment

Since the air conditioning apparatus 1 b can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 b can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 b is provided with the low-pressure receiver 41, liquid compression in the compressor 21 can be suppressed. Furthermore, since superheating control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38 during cooling operation and subcooling control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38 during heating operation, the capacities of the first indoor heat exchanger 31 and the second indoor heat exchanger 36 are likely sufficiently provided.

(3-4) Fourth Embodiment

An air conditioning apparatus 1 c serving as a refrigeration cycle apparatus according to a fourth embodiment is described below with reference to FIG. 3G which is a schematic configuration diagram of a refrigerant circuit and FIG. 3H which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 a according to the second embodiment are mainly described below.

(3-4-1) Schematic Configuration of Air Conditioning Apparatus 1 c

The air conditioning apparatus 1 c differs from the air conditioning apparatus 1 a according to the second embodiment in that the outdoor unit 20 does not include the low-pressure receiver 41, but includes a high-pressure receiver 42 and an outdoor bridge circuit 26.

Moreover, the indoor unit 30 includes an indoor liquid-side heat-exchange temperature sensor 71 that detects the temperature of the refrigerant flowing through the liquid side of the indoor heat exchanger 31, an indoor air temperature sensor 72 that detects the temperature of indoor air, and an indoor gas-side heat-exchange temperature sensor 73 that detects the temperature of the refrigerant flowing through the gas side of the indoor heat exchanger 31.

The outdoor bridge circuit 26 is provided between the liquid side of the outdoor heat exchanger 23 and the liquid-side shutoff valve 29, and has four connection portions and check valves provided between the connection portions. Refrigerant pipes extending to the high-pressure receiver 42 are connected to two portions that are included in the four connection portions of the outdoor bridge circuit 26 and that are other than a portion connected to the liquid side of the outdoor heat exchanger 23 and a portion connected to the liquid-side shutoff valve 29. The outdoor expansion valve 24 is provided midway in a refrigerant pipe that is included in the aforementioned refrigerant pipes and that extends from a gas region of the inner space of the high-pressure receiver 42.

(3-4-2) Cooling Operating Mode

In the air conditioning apparatus 1 c, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72). The evaporation temperature is not limited; however, may be recognized as, for example, the detected temperature of the indoor liquid-side heat-exchange temperature sensor 71, or the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63.

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 flows into the high-pressure receiver 42 via a portion of the outdoor bridge circuit 26. Note that the high-pressure receiver 42 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The gas refrigerant which has flowed out from the gas region of the high-pressure receiver 42 is decompressed in the outdoor expansion valve 24.

In this case, the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the indoor heat exchanger 31 or the degree of superheating of the refrigerant flowing through the suction side of the compressor 21 becomes a target value. Although not limited, the degree of superheating of the refrigerant flowing through the gas-side outlet of the indoor heat exchanger 31 may be obtained by subtracting the saturation temperature of the refrigerant corresponding to a low pressure of the refrigerant circuit 10 (the detected pressure of the suction pressure sensor 63) from the detected temperature of the indoor gas-side heat-exchange temperature sensor 73. Alternatively, the degree of superheating of the refrigerant flowing through the suction side of the compressor 21 may be obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 passes through anther portion of the outdoor bridge circuit 26, passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, flows into the indoor unit 30, and is evaporated in the indoor heat exchanger 31. The refrigerant which has flowed through the indoor heat exchanger 31 passes through the gas-side connection pipe 5, the gas-side shutoff valve 28, and the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-4-3) Heating Operating Mode

In the air conditioning apparatus 1 c, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72). The condensation temperature is not limited; however, may be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, then flows into the gas-side end of the indoor heat exchanger 31 of the indoor unit 30, and is condensed in the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows through the liquid-side connection pipe 6, flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, flows through a portion of the outdoor bridge circuit 26, and flows into the high-pressure receiver 42. Note that the high-pressure receiver 42 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The gas refrigerant which has flowed out from the gas region of the high-pressure receiver 42 is decompressed to a low pressure in the refrigeration cycle at the outdoor expansion valve 24.

Note that the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. The degree of superheating of the refrigerant flowing through the suction side of the compressor 21 is not limited, however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 flows through another portion of the outdoor bridge circuit 26, is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-4-4) Characteristics of Fourth Embodiment

Since the air conditioning apparatus 1 c can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 c can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 c is provided with the high-pressure receiver 42, an excessive refrigerant in the refrigerant circuit 10 can be stored.

(3-5) Fifth Embodiment

An air conditioning apparatus 1 d serving as a refrigeration cycle apparatus according to a fifth embodiment is described below with reference to FIG. 3I which is a schematic configuration diagram of a refrigerant circuit and FIG. 3J which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 c according to the fourth embodiment are mainly described below.

(3-5-1) Schematic Configuration of Air Conditioning Apparatus 1 d

The air conditioning apparatus 1 d differs from the air conditioning apparatus 1 c according to the fourth embodiment in that a plurality of indoor units are provided in parallel and an indoor expansion valve is provided on the liquid-refrigerant side of an indoor heat exchanger in each indoor unit.

The air conditioning apparatus 1 d includes a first indoor unit 30 and a second indoor unit 35 connected in parallel to each other. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor heat exchanger 31 and a first indoor fan 32, and a first indoor expansion valve 33 is provided on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor expansion valve 33 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor-unit control unit 34; and a first indoor liquid-side heat-exchange temperature sensor 71, a first indoor air temperature sensor 72, and a first indoor gas-side heat-exchange temperature sensor 73 that are electrically connected to the first indoor-unit control unit 34. The first indoor liquid-side heat-exchange temperature sensor 71 detects the temperature of the refrigerant flowing through the outlet on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor gas-side heat-exchange temperature sensor 73 detects the temperature of the refrigerant flowing through the outlet on the gas-refrigerant side of the first indoor heat exchanger 31. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor heat exchanger 36 and a second indoor fan 37, and a second indoor expansion valve 38 is provided on the liquid-refrigerant side of the second indoor heat exchanger 36. The second indoor expansion valve 38 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor-unit control unit 39, and a second indoor liquid-side heat-exchange temperature sensor 75, a second indoor air temperature sensor 76, and a second indoor gas-side heat-exchange temperature sensor 77 that are electrically connected to the second indoor-unit control unit 39.

(3-5-2) Cooling Operating Mode

In the air conditioning apparatus 1 c, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 flows into the high-pressure receiver 42 via a portion of the outdoor bridge circuit 26. Note that the high-pressure receiver 42 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The gas refrigerant which has flowed out from the gas region of the high-pressure receiver 42 is decompressed in the outdoor expansion valve 24. In this case, during cooling operation, the outdoor expansion valve 24 is controlled such that, for example, the valve opening degree becomes a full-open state.

The refrigerant which has passed through the outdoor expansion valve 24 passes through anther portion of the outdoor bridge circuit 26, passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and flows into the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is decompressed at the first indoor expansion valve 33. The valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the first indoor heat exchanger 31 becomes a target value. Although not limited, the degree of superheating of the refrigerant flowing through the gas-side outlet of the first indoor heat exchanger 31 may be obtained by subtracting the saturation temperature of the refrigerant corresponding to a low pressure of the refrigerant circuit 10 (the detected pressure of the suction pressure sensor 63) from the detected temperature of the first indoor gas-side heat-exchange temperature sensor 73. Likewise, the refrigerant which has flowed into the second indoor unit 35 is decompressed at the second indoor expansion valve 38. The valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the second indoor heat exchanger 36 becomes a target value. Although not limited, for example, the degree of superheating of the refrigerant flowing through the gas-side outlet of the second indoor heat exchanger 36 may be obtained by subtracting the saturation temperature of the refrigerant corresponding to a low pressure of the refrigerant circuit 10 (the detected pressure of the suction pressure sensor 63) from the detected temperature of the second indoor gas-side heat-exchange temperature sensor 77. Each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 may be controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Furthermore, the method of controlling each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant evaporated in the first indoor heat exchanger 31 and the refrigerant evaporated in the second indoor heat exchanger 36 are joined. Then, the joined refrigerant passes through the gas-side connection pipe 5, the gas-side shutoff valve 28, and the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-5-3) Heating Operating Mode

In the air conditioning apparatus 1 c, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load). The condensation temperature is not limited; however, may be recognized as, for example, the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61.

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, and then flows into each of the first indoor unit 30 and the second indoor unit 35.

The gas refrigerant which has flowed into the first indoor heat exchanger 31 of the first indoor unit 30 is condensed in the first indoor heat exchanger 31. The refrigerant which has flowed through the first indoor heat exchanger 31 is decompressed at the first indoor expansion valve 33. The valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first indoor heat exchanger 31 becomes a target value. The degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first indoor heat exchanger 31 can be obtained, for example, by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61 from the detected temperature of the first indoor liquid-side heat-exchange temperature sensor 71.

The gas refrigerant which has flowed into the second indoor heat exchanger 36 of the second indoor unit 35 is condensed in the second indoor heat exchanger 36 likewise. The refrigerant which has flowed through the second indoor heat exchanger 36 is decompressed at the second indoor expansion valve 38. The valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second indoor heat exchanger 36 becomes a target value. The degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second indoor heat exchanger 36 can be obtained, for example, by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the discharge pressure sensor 61 from the detected temperature of the second indoor liquid-side heat-exchange temperature sensor 75.

The refrigerant which has flowed out from the liquid-side end of the first indoor heat exchanger 31 and the refrigerant which has flowed out from the liquid-side end of the second indoor heat exchanger 36 are joined. Then, the joined refrigerant passes through the liquid-side connection pipe 6 and flows into the outdoor unit 20.

The refrigerant which has flowed into the outdoor unit 20 passes through the liquid-side shutoff valve 29, flows through a portion of the outdoor bridge circuit 26, and flows into the high-pressure receiver 42. Note that the high-pressure receiver 42 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The gas refrigerant which has flowed out from the gas region of the high-pressure receiver 42 is decompressed to a low pressure in the refrigeration cycle at the outdoor expansion valve 24. That is, during heating operation, the high-pressure receiver 42 stores a pseudo-intermediate-pressure refrigerant.

Note that the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. The degree of superheating of the refrigerant to be sucked by the compressor 21 is not limited however, for example, can be obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 flows through another portion of the outdoor bridge circuit 26, is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-5-4) Characteristics of Fifth Embodiment

Since the air conditioning apparatus 1 d can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 d can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 d is provided with the high-pressure receiver 42, an excessive refrigerant in the refrigerant circuit 10 can be stored.

During heating operation, since superheating control is performed on the valve opening degree of the outdoor expansion valve 24 to ensure reliability of the compressor 21. Thus, subcooling control can be performed on the first indoor expansion valve 33 and the second indoor expansion valve 38 to sufficiently provide the capacities of the first indoor heat exchanger 31 and the second indoor heat exchanger 36.

(3-6) Sixth Embodiment

An air conditioning apparatus 1 e serving as a refrigeration cycle apparatus according to a sixth embodiment is described below with reference to FIG. 3K which is a schematic configuration diagram of a refrigerant circuit and FIG. 3L which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 a according to the second embodiment are mainly described below.

(3-6-1) Schematic Configuration of Air Conditioning Apparatus 1 e

The air conditioning apparatus 1 e differs from the air conditioning apparatus 1 a according to the second embodiment in that the outdoor unit 20 does not include the low-pressure receiver 41, but includes an intermediate-pressure receiver 43 and does not include the outdoor expansion valve 24, but includes a first outdoor expansion valve 44 and a second outdoor expansion valve 45.

The intermediate-pressure receiver 43 is a refrigerant container that is provided between the liquid side of the outdoor heat exchanger 23 and the liquid-side shutoff valve 29 in the refrigerant circuit 10 and that can store, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10.

The first outdoor expansion valve 44 is provided midway in a refrigerant pipe extending from the liquid side of the outdoor heat exchanger 23 to the intermediate-pressure receiver 43. The second outdoor expansion valve 45 is provided midway in a refrigerant pipe extending from the intermediate-pressure receiver 43 to the liquid-side shutoff valve 29. The first outdoor expansion valve 44 and the second outdoor expansion valve 45 are each preferably an electric expansion valve of which the valve opening degree is adjustable.

(3-6-2) Cooling Operating Mode

In the air conditioning apparatus 1 e, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and then is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 is decompressed at the first outdoor expansion valve 44 to an intermediate pressure in the refrigeration cycle.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the outdoor heat exchanger 23 becomes a target value.

The refrigerant decompressed at the first outdoor expansion valve 44 flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The refrigerant which has passed through the intermediate-pressure receiver 43 is decompressed to a low pressure in the refrigeration cycle at the second outdoor expansion valve 45.

In this case, the valve opening degree of the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the second outdoor expansion valve 45 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the second outdoor expansion valve 45 to the low pressure in the refrigeration cycle passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, flows into the indoor unit 30, and is evaporated in the indoor heat exchanger 31. The refrigerant which has flowed through the indoor heat exchanger 31 flows through the gas-side connection pipe 5, then passes through the gas-side shutoff valve 28 and the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-6-3) Heating Operating Mode

In the air conditioning apparatus 1 e, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, then flows into the gas-side end of the indoor heat exchanger 31 of the indoor unit 30, and is condensed in the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows through the liquid-side connection pipe 6, flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, and is decompressed to an intermediate pressure in the refrigeration cycle at the second outdoor expansion valve 45.

In this case, the valve opening degree of the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the indoor heat exchanger 31 becomes a target value.

The refrigerant decompressed at the second outdoor expansion valve 45 flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The refrigerant which has passed through the intermediate-pressure receiver 43 is decompressed to a low pressure in the refrigeration cycle at the first outdoor expansion valve 44.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the first outdoor expansion valve 44 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first outdoor expansion valve 44 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and is sucked into the compressor 21 again.

(3-6-4) Characteristics of Sixth Embodiment

Since the air conditioning apparatus 1 e can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 e can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 e is provided with the intermediate-pressure receiver 43, an excessive refrigerant in the refrigerant circuit 10 can be stored. During cooling operation, since subcooling control is performed on the first outdoor expansion valve 44, the capacity of the outdoor heat exchanger 23 can be likely sufficiently provided. During heating operation, since subcooling control is performed on the second outdoor expansion valve 45, the capacity of the indoor heat exchanger 31 can be likely sufficiently provided.

(3-7) Seventh Embodiment

An air conditioning apparatus if serving as a refrigeration cycle apparatus according to a seventh embodiment is described below with reference to FIG. 3M which is a schematic configuration diagram of a refrigerant circuit and FIG. 3N which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 e according to the sixth embodiment are mainly described below.

(3-7-1) Schematic Configuration of Air Conditioning Apparatus 1 f

The air conditioning apparatus 1 f differs from the air conditioning apparatus 1 e according to the sixth embodiment in that the outdoor unit 20 includes a first outdoor heat exchanger 23 a and a second outdoor heat exchanger 23 b disposed in parallel to each other, includes a first branch outdoor expansion valve 24 a on the liquid-refrigerant side of the first outdoor heat exchanger 23 a, and includes a second branch outdoor expansion valve 24 b on the liquid-refrigerant side of the second outdoor heat exchanger 23 b. The first branch outdoor expansion valve 24 a and the second branch outdoor expansion valve 24 b are each preferably an electric expansion valve of which the valve opening degree is adjustable.

Moreover, the air conditioning apparatus if differs from the air conditioning apparatus 1 e according to the sixth embodiment in that a plurality of indoor units are provided in parallel and an indoor expansion valve is provided on the liquid-refrigerant side of an indoor heat exchanger in each indoor unit.

The air conditioning apparatus if includes a first indoor unit 30 and a second indoor unit 35 connected in parallel to each other. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor heat exchanger 31 and a first indoor fan 32, and a first indoor expansion valve 33 is provided on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor expansion valve 33 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor-unit control unit 34, and a first indoor liquid-side heat-exchange temperature sensor 71, a first indoor air temperature sensor 72, and a first indoor gas-side heat-exchange temperature sensor 73 that are electrically connected to the first indoor-unit control unit 34. The first indoor liquid-side heat-exchange temperature sensor 71 detects the temperature of the refrigerant flowing through the outlet on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor gas-side heat-exchange temperature sensor 73 detects the temperature of the refrigerant flowing through the outlet on the gas-refrigerant side of the first indoor heat exchanger 31. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor heat exchanger 36 and a second indoor fan 37, and a second indoor expansion valve 38 is provided on the liquid-refrigerant side of the second indoor heat exchanger 36. The second indoor expansion valve 38 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor-unit control unit 39, and a second indoor liquid-side heat-exchange temperature sensor 75, a second indoor air temperature sensor 76, and a second indoor gas-side heat-exchange temperature sensor 77 that are electrically connected to the second indoor-unit control unit 39.

(3-7-2) Cooling Operating Mode

In the air conditioning apparatus 1 f, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22, then is branched and flows to the first outdoor heat exchanger 23 a and the second outdoor heat exchanger 23 b, and the respective branched refrigerants are condensed in the first outdoor heat exchanger 23 a and the second outdoor heat exchanger 23 b. The refrigerant which has flowed through the first outdoor heat exchanger 23 a is decompressed at the first branch outdoor expansion valve 24 a to an intermediate pressure in the refrigeration cycle. The refrigerant which has flowed through the second outdoor heat exchanger 23 b is decompressed at the second branch outdoor expansion valve 24 b to an intermediate pressure in the refrigeration cycle.

In this case, each of the first branch outdoor expansion valve 24 a and the second branch outdoor expansion valve 24 b may be controlled, for example, to be in a full-open state.

Moreover, when the first outdoor heat exchanger 23 a and the second outdoor heat exchanger 23 b have a difference in easiness of flowing of the refrigerant due to the structure thereof or the connection of refrigerant pipes, the valve opening degree of the first branch outdoor expansion valve 24 a may be controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first outdoor heat exchanger 23 a becomes a common target value, and the valve opening degree of the second branch outdoor expansion valve 24 b may be controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second outdoor heat exchanger 23 b becomes a common target value. With the control, an uneven flow of the refrigerant between the first outdoor heat exchanger 23 a and the second outdoor heat exchanger 23 b can be minimized.

The refrigerant which has passed through the first branch outdoor expansion valve 24 a and the refrigerant which has passed through the second branch outdoor expansion valve 24 b are joined. Then, the joined refrigerant flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The refrigerant which has passed through the intermediate-pressure receiver 43 flows through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and flows into each of the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is decompressed at the first indoor expansion valve 33 to a low pressure in the refrigeration cycle. The refrigerant which has flowed into the second indoor unit 35 is decompressed at the second indoor expansion valve 38 to a low pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the first indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Moreover, likewise, the valve opening degree of the second indoor expansion valve 38 is also controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the second indoor heat exchanger 36 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first indoor expansion valve 33 is evaporated in the first indoor heat exchanger 31, the refrigerant decompressed at the second indoor expansion valve 38 is evaporated in the second indoor heat exchanger 36, and the evaporated refrigerants are joined. Then, the joined refrigerant passes through the gas-side connection pipe 5, the gas-side shutoff valve 28, and the four-way switching valve 22, and is sucked by the compressor 21 again.

(3-7-3) Heating Operating Mode

In the air conditioning apparatus if, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, and then flows into each of the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is condensed in the first indoor heat exchanger 31. The refrigerant which has flowed into the second indoor unit 35 is condensed in the second indoor heat exchanger 36.

The refrigerant which has flowed out from the liquid-side end of the first indoor heat exchanger 31 is decompressed at the first indoor expansion valve 33 to an intermediate pressure in the refrigeration cycle. The refrigerant which has flowed out from the second indoor heat exchanger 36 is decompressed at the second indoor expansion valve 38 to an intermediate pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first indoor heat exchanger 31 becomes a target value. Also, the valve opening degree of the second indoor expansion valve 38 is controlled likewise to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second indoor heat exchanger 36 becomes a target value.

The refrigerant which has passed through the first indoor expansion valve 33 and the refrigerant which has passed through the second indoor expansion valve 38 are joined. Then, the joined refrigerant passes through the liquid-side connection pipe 6 and flows into the outdoor unit 20.

The refrigerant which has flowed into the outdoor unit 20 passes through the liquid-side shutoff valve 29, and is sent to the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. The refrigerant which has passed through the intermediate-pressure receiver 43 flows in a separated manner to the first branch outdoor expansion valve 24 a and the second branch outdoor expansion valve 24 b.

The first branch outdoor expansion valve 24 a decompresses the passing refrigerant to a low pressure in the refrigeration cycle. The second branch outdoor expansion valve 24 b similarly decompresses the passing refrigerant to a low pressure in the refrigeration cycle.

In this case, each of the valve opening degrees of the first branch outdoor expansion valve 24 a and the second branch outdoor expansion valve 24 b is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling each of the valve opening degrees of the first branch outdoor expansion valve 24 a and the second branch outdoor expansion valve 24 b is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first branch outdoor expansion valve 24 a is evaporated in the first outdoor heat exchanger 23 a, the refrigerant decompressed at the second branch outdoor expansion valve 24 b is evaporated in the second outdoor heat exchanger 23 b, and the evaporated refrigerants are joined. Then, the joined refrigerant passes through the four-way switching valve 22 and is sucked by the compressor 21 again.

(3-7-4) Characteristics of Seventh Embodiment

Since the air conditioning apparatus if can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 f can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus if is provided with the intermediate-pressure receiver 43, an excessive refrigerant in the refrigerant circuit 10 can be stored. During heating operation, since subcooling control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38, the capacity of the indoor heat exchanger 31 can be likely sufficiently provided.

(3-8) Eighth Embodiment

An air conditioning apparatus 1 g serving as a refrigeration cycle apparatus according to an eighth embodiment is described below with reference to FIG. 3O which is a schematic configuration diagram of a refrigerant circuit and FIG. 3P which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 b according to the third embodiment are mainly described below.

(3-8-1) Schematic Configuration of Air Conditioning Apparatus 1 g

The air conditioning apparatus 1 g differs from the air conditioning apparatus 1 b according to the third embodiment in that the bypass pipe 40 having the bypass expansion valve 49 is not provided, a subcooling heat exchanger 47 is provided, a subcooling pipe 46 is provided, a first outdoor expansion valve 44 and a second outdoor expansion valve 45 are provided, and a subcooling temperature sensor 67 is provided.

The first outdoor expansion valve 44 is provided between the liquid-side outlet of the outdoor heat exchanger 23 and the liquid-side shutoff valve 29 in the refrigerant circuit 10. The second outdoor expansion valve 45 is provided between the first outdoor expansion valve 44 and the liquid-side shutoff valve 29 in the refrigerant circuit 10. The first outdoor expansion valve 44 and the second outdoor expansion valve 45 are each preferably an electric expansion valve of which the valve opening degree is adjustable.

The subcooling pipe 46 is, in the refrigerant circuit 10, branched from a branch portion between the first outdoor expansion valve 44 and the second outdoor expansion valve 45, and is joined to a joint portion between one of the connecting ports of the four-way switching valve 22 and the low-pressure receiver 41. The subcooling pipe 46 is provided with a subcooling expansion valve 48. The subcooling expansion valve 48 is preferably an electric expansion valve of which the valve opening degree is adjustable.

The subcooling heat exchanger 47 is, in the refrigerant circuit 10, a heat exchanger that causes the refrigerant flowing through the portion between the first outdoor expansion valve 44 and the second outdoor expansion valve 45 and the refrigerant flowing through a portion on the joint portion side of the subcooling expansion valve 48 in the subcooling pipe 46 to exchange heat with each other. In the present embodiment, the subcooling heat exchanger 47 is provided in a portion that is between the first outdoor expansion valve 44 and the second outdoor expansion valve 45 and that is on the side closer than the branch portion of the subcooling pipe 46 to the second outdoor expansion valve 45.

The subcooling temperature sensor 67 is a temperature sensor that detects the temperature of the refrigerant flowing through a portion closer than the subcooling heat exchanger 47 to the second outdoor expansion valve 45 in a portion between the first outdoor expansion valve 44 and the second outdoor expansion valve 45 in the refrigerant circuit 10.

(3-8-2) Cooling Operating Mode

In the air conditioning apparatus 1 g, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 passes through the first outdoor expansion valve 44. Note that, in this case, the first outdoor expansion valve 44 is controlled to be in a full-open state.

A portion of the refrigerant which has passed through the first outdoor expansion valve 44 flows toward the second outdoor expansion valve 45 and another portion of the refrigerant is branched and flows to the subcooling pipe 46. The refrigerant which has been branched and flowed to the subcooling pipe 46 is decompressed at the subcooling expansion valve 48. The subcooling heat exchanger 47 causes the refrigerant flowing from the first outdoor expansion valve 44 toward the second outdoor expansion valve 45, and the refrigerant decompressed at the subcooling expansion valve 48 and flowing through the subcooling pipe 46 to exchange heat with each other. The refrigerant flowing through the subcooling pipe 46 exchanges heat in the subcooling heat exchanger 47, and then flows to join to a joint portion extending from one of the connecting ports of the four-way switching valve 22 to the low-pressure receiver 41. After the heat exchange in the subcooling heat exchanger 47, the refrigerant flowing from the first outdoor expansion valve 44 toward the second outdoor expansion valve 45 is decompressed at the second outdoor expansion valve 45.

As described above, the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the outdoor heat exchanger 23 becomes a target value.

Moreover, the valve opening degree of the subcooling expansion valve 48 is controlled such that at least the refrigerant which reaches the first indoor expansion valve 33 and the second indoor expansion valve 38 is in a gas-liquid two-phase state to prevent occurrence of a situation in which all portions extending from the second outdoor expansion valve 45 via the liquid-side connection pipe 6 to the first indoor expansion valve 33 and the second indoor expansion valve 38 are filled with the refrigerant in a liquid state in the refrigerant circuit 10. For example, the valve opening degree of the subcooling expansion valve 48 is preferably controlled such that the specific enthalpy of the refrigerant which flows from the first outdoor expansion valve 44 toward the second outdoor expansion valve 45 and which has passed through the subcooling heat exchanger 47 is larger than the specific enthalpy of a portion in which the low pressure in the refrigeration cycle intersects with the saturated liquid line in the Mollier diagram. In this case, the controller 7 previously stores data in the Mollier diagram corresponding to the refrigerant, and may control the valve opening degree of the subcooling expansion valve 48 based of the specific enthalpy of the refrigerant which has passed through the subcooling heat exchanger 47 acquired from the detected pressure of the discharge pressure sensor 61, the detected temperature of the subcooling temperature sensor 67, and the data of the Mollier diagram corresponding to the refrigerant. The valve opening degree of the subcooling expansion valve 48 is preferably controlled to satisfy a predetermined condition, for example, such that the temperature of the refrigerant which flows from the first outdoor expansion valve 44 toward the second outdoor expansion valve 45 and which has passed through the subcooling heat exchanger 47 (the detected temperature of the subcooling temperature sensor 67) becomes a target value.

The refrigerant decompressed at the second outdoor expansion valve 45 passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and is sent to the first indoor unit 30 and the second indoor unit 35.

In this case, in the first indoor unit 30, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the first indoor heat exchanger 31 becomes a target value. Moreover, also for the second indoor expansion valve 38 of the second indoor unit 35, similarly to the first indoor expansion valve 33, the valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas-side outlet of the second indoor heat exchanger 36 becomes a target value. Each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 may be controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant obtained by subtracting the saturation temperature of the refrigerant corresponding to the detected pressure of the suction pressure sensor 63 from the detected temperature of the suction temperature sensor 64. Furthermore, the method of controlling each of the valve opening degrees of the first indoor expansion valve 33 and the second indoor expansion valve 38 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first indoor expansion valve 33 is evaporated in the first indoor heat exchanger 31, the refrigerant decompressed at the second indoor expansion valve 38 is evaporated in the second indoor heat exchanger 36, and the evaporated refrigerants are joined. Then, the joined refrigerant flows to the gas-side connection pipe 5. The refrigerant which has flowed through the gas-side connection pipe 5 passes through the gas-side shutoff valve 28 and the four-way switching valve 22, and is joined to the refrigerant which has flowed through the subcooling pipe 46. The joined refrigerant passes through the low-pressure receiver 41 and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerants which have not been completely evaporated in the first indoor heat exchanger 31, the second indoor heat exchanger 36, and the subcooling heat exchanger 47.

(3-8-3) Heating Operating Mode

In the air conditioning apparatus 1 g, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5 then a portion of the refrigerant flows into the gas-side end of the first indoor heat exchanger 31 of the first indoor unit 30 and is condensed in the first indoor heat exchanger 31, and another portion of the refrigerant flows into the gas-side end of the second indoor heat exchanger 36 of the second indoor unit 35 and is condensed in the second indoor heat exchanger 36.

Note that, the valve opening degree of the first indoor expansion valve 33 of the first indoor unit 30 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid side of the first indoor heat exchanger 31 becomes a predetermined target value. Also for the second indoor expansion valve 38 of the second indoor unit 35, the valve opening degree of the second indoor expansion valve 38 is controlled likewise to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid side of the second indoor heat exchanger 36 becomes a predetermined target value.

The refrigerant decompressed at the first indoor expansion valve 33 and the refrigerant decompressed at the second indoor expansion valve 38 are joined. The joined refrigerant flows through the liquid-side connection pipe 6 and flows into the outdoor unit 20.

The refrigerant which has passed through the liquid-side shutoff valve 29 of the outdoor unit 20 passes through the second outdoor expansion valve 45 controlled to be in a full-open state, and exchanges heat with the refrigerant flowing through the subcooling pipe 46 in the subcooling heat exchanger 47. A portion of the refrigerant which has passed through the second outdoor expansion valve 45 and the subcooling heat exchanger 47 is branched to the subcooling pipe 46, and another portion of the refrigerant is sent to the first outdoor expansion valve 44. The refrigerant which has been branched and flowed to the subcooling pipe 46 is decompressed at the subcooling expansion valve 48, and then is joined to the refrigerant which has flowed from the indoor unit 30 or 35, in a joint portion between one of the connecting ports of the four-way switching valve 22 and the low-pressure receiver 41. The refrigerant which has flowed from the subcooling heat exchanger 47 toward the first outdoor expansion valve 44 is decompressed at the first outdoor expansion valve 44, and flows into the outdoor heat exchanger 23.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the suction side of the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the first outdoor expansion valve 44 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

Moreover, the valve opening degree of the subcooling expansion valve 48 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the suction side of the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the subcooling expansion valve 48 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition. During heating operation, the subcooling expansion valve 48 may be controlled to be in a full-close state to prevent the refrigerant from flowing to the subcooling pipe 46.

The refrigerant decompressed at the first outdoor expansion valve 44 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and is joined to the refrigerant which has flowed through the subcooling pipe 46. The joined refrigerant passes through the low-pressure receiver 41 and is sucked into the compressor 21 again. Note that the low-pressure receiver 41 stores, as an excessive refrigerant, the liquid refrigerant which has not been completely evaporated in the outdoor heat exchanger 23 and the subcooling heat exchanger 47.

(3-8-4) Characteristics of Eighth Embodiment

Since the air conditioning apparatus 1 g can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 g can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 g is provided with the low-pressure receiver 41, liquid compression in the compressor 21 can be suppressed. Furthermore, since superheating control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38 during cooling operation and subcooling control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38 during heating operation, the capacities of the first indoor heat exchanger 31 and the second indoor heat exchanger 36 are likely sufficiently provided.

Furthermore, with the air conditioning apparatus 1 g, during cooling operation, the space in the pipes from when the refrigerant passes through the second outdoor expansion valve 45 to when the refrigerant reaches the first indoor expansion valve 33 and the second indoor expansion valve 38 via the liquid-side connection pipe 6 is not filled with the liquid-state refrigerant, and control is performed so that a refrigerant in a gas-liquid two-phase state is in at least a portion of the space. As compared with the case where all the space in the pipes extending from the second outdoor expansion valve 45 to the first indoor expansion valve 33 and the second indoor expansion valve 38 is filled with the liquid refrigerant, refrigerant concentration can be decreased in the portion. The refrigeration cycle can be performed while the amount of refrigerant enclosed in the refrigerant circuit 10 is decreased. Thus, even if the refrigerant leaks from the refrigerant circuit 10, the leakage amount of refrigerant can be decreased.

(3-9) Ninth Embodiment

An air conditioning apparatus 1 h serving as a refrigeration cycle apparatus according to a ninth embodiment is described below with reference to FIG. 3Q which is a schematic configuration diagram of a refrigerant circuit and FIG. 3R which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 e according to the sixth embodiment are mainly described below.

(3-9-1) Schematic Configuration of Air Conditioning Apparatus 1 h

The air conditioning apparatus 1 h differs from the air conditioning apparatus 1 e according to the sixth embodiment in that a suction refrigerant heating section 50 is included.

The suction refrigerant heating section 50 is constituted of a portion of the refrigerant pipe that extends from one of the connecting ports of the four-way switching valve 22 toward the suction side of the compressor 21 and that is located in the intermediate-pressure receiver 43. In the suction refrigerant heating section 50, the refrigerant flowing through the refrigerant pipe that extends from one of the connecting ports of the four-way switching valve 22 toward the suction side of the compressor 21 and the refrigerant in the intermediate-pressure receiver 43 exchange heat with each other without mixed with each other.

(3-9-2) Cooling Operating Mode

In the air conditioning apparatus 1 h, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and then is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 is decompressed at the first outdoor expansion valve 44 to an intermediate pressure in the refrigeration cycle.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the outdoor heat exchanger 23 becomes a target value.

The refrigerant decompressed at the first outdoor expansion valve 44 flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. In this case, the refrigerant which has flowed into the intermediate-pressure receiver 43 is cooled through heat exchange with the refrigerant flowing through a portion of the suction refrigerant heating section 50 on the suction side of the compressor 21. The refrigerant which has cooled in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43 is decompressed to a low pressure in the refrigeration cycle at the second outdoor expansion valve 45.

In this case, the valve opening degree of the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the second outdoor expansion valve 45 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the second outdoor expansion valve 45 to the low pressure in the refrigeration cycle passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, flows into the indoor unit 30, and is evaporated in the indoor heat exchanger 31. The refrigerant which has flowed through the indoor heat exchanger 31 flows through the gas-side connection pipe 5, then passes through the gas-side shutoff valve 28 and the four-way switching valve 22, and flows inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43. The refrigerant flowing inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43 is heated through heat exchange with the refrigerant stored in the intermediate-pressure receiver 43, in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43, and is sucked into the compressor 21 again.

(3-9-3) Heating Operating Mode

In the air conditioning apparatus 1 h, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, then flows into the gas-side end of the indoor heat exchanger 31 of the indoor unit 30, and is condensed in the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows through the liquid-side connection pipe 6, flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, and is decompressed to an intermediate pressure in the refrigeration cycle at the second outdoor expansion valve 45.

In this case, the valve opening degree of the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the indoor heat exchanger 31 becomes a target value.

The refrigerant decompressed at the second outdoor expansion valve 45 flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. In this case, the refrigerant which has flowed into the intermediate-pressure receiver 43 is cooled through heat exchange with the refrigerant flowing through a portion of the suction refrigerant heating section 50 on the suction side of the compressor 21. The refrigerant which has cooled in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43 is decompressed to a low pressure in the refrigeration cycle at the first outdoor expansion valve 44.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the first outdoor expansion valve 44 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first outdoor expansion valve 44 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and flows inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43. The refrigerant flowing inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43 is heated through heat exchange with the refrigerant stored in the intermediate-pressure receiver 43, in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43, and is sucked into the compressor 21 again.

(3-9-4) Characteristics of Ninth Embodiment

Since the air conditioning apparatus 1 h can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 h can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 h is provided with the intermediate-pressure receiver 43, an excessive refrigerant in the refrigerant circuit 10 can be stored. During cooling operation, since subcooling control is performed on the first outdoor expansion valve 44, the capacity of the outdoor heat exchanger 23 can be likely sufficiently provided. During heating operation, since subcooling control is performed on the second outdoor expansion valve 45, the capacity of the indoor heat exchanger 31 can be likely sufficiently provided.

Furthermore, since the suction refrigerant heating section 50 is provided, the refrigerant to be sucked into the compressor 21 is heated and liquid compression in the compressor 21 is suppressed. Control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the indoor heat exchanger 31 that functions as the evaporator of the refrigerant during cooling operation to be a small value. Also, similarly in heating operation, control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the outdoor heat exchanger 23 that functions as the evaporator of the refrigerant to be a small value. Thus, in either of cooling operation and heating operation, even when use of a nonazeotropic mixed refrigerant as the refrigerant causes a temperature glide in the evaporator, the capacity of the heat exchanger that functions as the evaporator can be sufficiently provided.

(3-10) Tenth Embodiment

An air conditioning apparatus 1 i serving as a refrigeration cycle apparatus according to a tenth embodiment is described below with reference to FIG. 3S which is a schematic configuration diagram of a refrigerant circuit and FIG. 3T which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 h according to the ninth embodiment are mainly described below.

(3-10-1) Schematic Configuration of Air Conditioning Apparatus 1 i

The air conditioning apparatus 1 i differs from the air conditioning apparatus 1 h according to the ninth embodiment in that the first outdoor expansion valve 44 and the second outdoor expansion valve 45 are not provided, the outdoor expansion valve 24 is provided, a plurality of indoor units (a first indoor unit 30 and a second indoor unit 35) are provided in parallel, and an indoor expansion valve is provided on the liquid-refrigerant side of an indoor heat exchanger in each indoor unit.

The outdoor expansion valve 24 is provided midway in a refrigerant pipe extending from the liquid-side outlet of the outdoor heat exchanger 23 to the intermediate-pressure receiver 43. The outdoor expansion valve 24 is preferably an electric expansion valve of which the valve opening degree is adjustable.

Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor heat exchanger 31 and a first indoor fan 32, and a first indoor expansion valve 33 is provided on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor expansion valve 33 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor-unit control unit 34; and a first indoor liquid-side heat-exchange temperature sensor 71, a first indoor air temperature sensor 72, and a first indoor gas-side heat-exchange temperature sensor 73 that are electrically connected to the first indoor-unit control unit 34. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor heat exchanger 36 and a second indoor fan 37, and a second indoor expansion valve 38 is provided on the liquid-refrigerant side of the second indoor heat exchanger 36. The second indoor expansion valve 38 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor-unit control unit 39; and a second indoor liquid-side heat-exchange temperature sensor 75, a second indoor air temperature sensor 76, and a second indoor gas-side heat-exchange temperature sensor 77 that are electrically connected to the second indoor-unit control unit 39.

(3-10-2) Cooling Operating Mode

In the air conditioning apparatus 1 i, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and then is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 passes through the outdoor expansion valve 24 controlled to be in a full-open state.

The refrigerant which has passed through the outdoor expansion valve 24 flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. In this case, the refrigerant which has flowed into the intermediate-pressure receiver 43 is cooled through heat exchange with the refrigerant flowing through a portion of the suction refrigerant heating section 50 on the suction side of the compressor 21. The refrigerant which has cooled in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43 passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, and flows into the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is decompressed at the first indoor expansion valve 33 to a low pressure in the refrigeration cycle. The refrigerant which has flowed into the second indoor unit 35 is decompressed at the second indoor expansion valve 38 to a low pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the first indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Moreover, the valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the second indoor heat exchanger 36 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value.

The refrigerant decompressed at the first indoor expansion valve 33 is evaporated in the first indoor heat exchanger 31, the refrigerant decompressed at the second indoor expansion valve 38 is evaporated in the second indoor heat exchanger 36, and the evaporated refrigerants are joined. Then, the joined refrigerant flows through the gas-side connection pipe 5, the gas-side shutoff valve 28, and the four-way switching valve 22, and flows inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43. The refrigerant flowing inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43 is heated through heat exchange with the refrigerant stored in the intermediate-pressure receiver 43, in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43, and is sucked into the compressor 21 again.

(3-10-3) Heating Operating Mode

In the air conditioning apparatus 1 i, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, and then flows into each of the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is condensed in the first indoor heat exchanger 31. The refrigerant which has flowed into the second indoor unit 35 is condensed in the second indoor heat exchanger 36.

The refrigerant which has flowed out from the liquid-side end of the first indoor heat exchanger 31 is decompressed at the first indoor expansion valve 33 to an intermediate pressure in the refrigeration cycle. The refrigerant which has flowed out from the liquid-side end of the second indoor heat exchanger 36 is decompressed at the second indoor expansion valve 38 to an intermediate pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first indoor heat exchanger 31 becomes a target value. Also, the valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second indoor heat exchanger 36 becomes a target value.

The refrigerant which has passed through the first indoor expansion valve 33 and the refrigerant which has passed through the second indoor expansion valve 38 are joined. Then, the joined refrigerant passes through the liquid-side connection pipe 6 and flows into the outdoor unit 20.

The refrigerant which has flowed into the outdoor unit 20 passes through the liquid-side shutoff valve 29, and flows into the intermediate-pressure receiver 43. The intermediate-pressure receiver 43 stores, as the liquid refrigerant, an excessive refrigerant in the refrigerant circuit 10. In this case, the refrigerant which has flowed into the intermediate-pressure receiver 43 is cooled through heat exchange with the refrigerant flowing through a portion of the suction refrigerant heating section 50 on the suction side of the compressor 21. The refrigerant which has cooled in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43 is decompressed to a low pressure in the refrigeration cycle at the outdoor expansion valve 24.

In this case, the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, and flows inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43. The refrigerant flowing inside the refrigerant pipe that passes through the inside of the intermediate-pressure receiver 43 is heated through heat exchange with the refrigerant stored in the intermediate-pressure receiver 43, in the suction refrigerant heating section 50 in the intermediate-pressure receiver 43, and is sucked into the compressor 21 again.

(3-10-4) Characteristics of Tenth Embodiment

Since the air conditioning apparatus 1 i can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 i can perform a refrigeration cycle using a small-GWP refrigerant.

Moreover, since the air conditioning apparatus 1 i is provided with the intermediate-pressure receiver 43, an excessive refrigerant in the refrigerant circuit 10 can be stored. During heating operation, since subcooling control is performed on the second outdoor expansion valve 45, the capacity of the indoor heat exchanger 31 can be likely sufficiently provided.

Furthermore, since the suction refrigerant heating section 50 is provided, the refrigerant to be sucked into the compressor 21 is heated and liquid compression in the compressor 21 is suppressed. Control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the indoor heat exchanger 31 that functions as the evaporator of the refrigerant during cooling operation to be a small value. Also, similarly in heating operation, control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the outdoor heat exchanger 23 that functions as the evaporator of the refrigerant to be a small value. Thus, in either of cooling operation and heating operation, even when use of a nonazeotropic mixed refrigerant as the refrigerant causes a temperature glide in the evaporator, the capacity of the heat exchanger that functions as the evaporator can be sufficiently provided.

(3-11) Eleventh Embodiment

An air conditioning apparatus 1 j serving as a refrigeration cycle apparatus according to an eleventh embodiment is described below with reference to FIG. 3U which is a schematic configuration diagram of a refrigerant circuit and FIG. 3V which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 h according to the ninth embodiment are mainly described below.

(3-11-1) Schematic Configuration of Air Conditioning Apparatus 1 j

The air conditioning apparatus 1 j differs from the air conditioning apparatus 1 h according to the ninth embodiment in that the suction refrigerant heating section 50 is not provided and an internal heat exchanger 51 is provided.

The internal heat exchanger 51 is a heat exchanger that exchanges heat between the refrigerant flowing between the first outdoor expansion valve 44 and the second outdoor expansion valve 45 and the refrigerant flowing through the refrigerant pipe extending from one of the connecting ports of the four-way switching valve 22 toward the suction side of the compressor 21.

(3-11-2) Cooling Operating Mode

In the air conditioning apparatus 1 j, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and then is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 passes through the first outdoor expansion valve 44 controlled to be in a full-open state. The refrigerant which has passed through the first outdoor expansion valve 44 is cooled in the internal heat exchanger 51 and decompressed to a low pressure in the refrigeration cycle at the second outdoor expansion valve 45.

In this case, the valve opening degree of the second outdoor expansion valve 45 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the second outdoor expansion valve 45 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the second outdoor expansion valve 45 to the low pressure in the refrigeration cycle passes through the liquid-side shutoff valve 29 and the liquid-side connection pipe 6, flows into the indoor unit 30, and is evaporated in the indoor heat exchanger 31. The refrigerant which has flowed through the indoor heat exchanger 31 flows through the gas-side connection pipe 5, then passes through the gas-side shutoff valve 28 and the four-way switching valve 22, is heated in the internal heat exchanger 51, and is sucked into the compressor 21 again.

(3-11-3) Heating Operating Mode

In the air conditioning apparatus 1 j, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature that is determined in accordance with the difference between the set temperature and the indoor temperature (the detected temperature of the indoor air temperature sensor 72).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, then flows into the gas-side end of the indoor heat exchanger 31 of the indoor unit 30, and is condensed in the indoor heat exchanger 31. The refrigerant which has flowed out from the liquid-side end of the indoor heat exchanger 31 flows through the liquid-side connection pipe 6, flows into the outdoor unit 20, passes through the liquid-side shutoff valve 29, and passes through the second outdoor expansion valve 45 controlled to be in a full-open state. The refrigerant which has passed through the second outdoor expansion valve 45 is cooled in the internal heat exchanger 51 and decompressed to an intermediate pressure in the refrigeration cycle at the first outdoor expansion valve 44.

In this case, the valve opening degree of the first outdoor expansion valve 44 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the first outdoor expansion valve 44 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the first outdoor expansion valve 44 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, is heated in the internal heat exchanger 51, and is sucked into the compressor 21 again.

(3-11-4) Characteristics of Eleventh Embodiment

Since the air conditioning apparatus 1 j can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 j can perform a refrigeration cycle using a small-GWP refrigerant.

Furthermore, since the air conditioning apparatus 1 j is provided with the internal heat exchanger 51, the refrigerant to be sucked into the compressor 21 is heated and liquid compression in the compressor 21 is suppressed. Control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the indoor heat exchanger 31 that functions as the evaporator of the refrigerant during cooling operation to be a small value.

Also, similarly in heating operation, control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the outdoor heat exchanger 23 that functions as the evaporator of the refrigerant to be a small value. Thus, in either of cooling operation and heating operation, even when use of a nonazeotropic mixed refrigerant as the refrigerant causes a temperature glide in the evaporator, the capacity of the heat exchanger that functions as the evaporator can be sufficiently provided.

(3-12) Twelfth Embodiment

An air conditioning apparatus 1 k serving as a refrigeration cycle apparatus according to a twelfth embodiment is described below with reference to FIG. 3W which is a schematic configuration diagram of a refrigerant circuit and FIG. 3X which is a schematic control block configuration diagram. Differences from the air conditioning apparatus 1 j according to the tenth embodiment are mainly described below.

(3-12-1) Schematic Configuration of Air Conditioning Apparatus 1 k

The air conditioning apparatus 1 k differs from the air conditioning apparatus 1 j according to the tenth embodiment in that the first outdoor expansion valve 44 and the second outdoor expansion valve 45 are not provided, but an outdoor expansion valve 24 is provided; a plurality of indoor units (a first indoor unit 30 and a second indoor unit 35) are provided in parallel; and an indoor expansion valve is provided on the liquid-refrigerant side of an indoor heat exchanger in each indoor unit.

The outdoor expansion valve 24 is provided midway in the refrigerant pipe extending from the internal heat exchanger 51 to the liquid-side shutoff valve 29. The outdoor expansion valve 24 is preferably an electric expansion valve of which the valve opening degree is adjustable.

Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor heat exchanger 31 and a first indoor fan 32, and a first indoor expansion valve 33 is provided on the liquid-refrigerant side of the first indoor heat exchanger 31. The first indoor expansion valve 33 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the above-described embodiment, the first indoor unit 30 includes a first indoor-unit control unit 34, and a first indoor liquid-side heat-exchange temperature sensor 71, a first indoor air temperature sensor 72, and a first indoor gas-side heat-exchange temperature sensor 73 that are electrically connected to the first indoor-unit control unit 34. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor heat exchanger 36 and a second indoor fan 37, and a second indoor expansion valve 38 is provided on the liquid-refrigerant side of the second indoor heat exchanger 36. The second indoor expansion valve 38 is preferably an electric expansion valve of which the valve opening degree is adjustable. Similarly to the first indoor unit 30, the second indoor unit 35 includes a second indoor-unit control unit 39, and a second indoor liquid-side heat-exchange temperature sensor 75, a second indoor air temperature sensor 76, and a second indoor gas-side heat-exchange temperature sensor 77 that are electrically connected to the second indoor-unit control unit 39.

(3-12-2) Cooling Operating Mode

In the air conditioning apparatus 1 k, in the cooling operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the evaporation temperature of the refrigerant in the refrigerant circuit 10 becomes a target evaporation temperature. In this case, the target evaporation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 passes through the four-way switching valve 22 and then is condensed in the outdoor heat exchanger 23. The refrigerant which has flowed through the outdoor heat exchanger 23 is cooled in the internal heat exchanger 51, passes through the outdoor expansion valve 24 controlled to be in a full-open state, passes through the liquid-side shutoff valve 29, and the liquid-side connection pipe 6, and flows into each of the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is decompressed at the first indoor expansion valve 33 to a low pressure in the refrigeration cycle. The refrigerant which has flowed into the second indoor unit 35 is decompressed at the second indoor expansion valve 38 to a low pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the first indoor heat exchanger 31 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Moreover, likewise, the valve opening degree of the second indoor expansion valve 38 is also controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant flowing through the gas side of the second indoor heat exchanger 36 or the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value.

The refrigerant decompressed at the first indoor expansion valve 33 is evaporated in the first indoor heat exchanger 31, the refrigerant decompressed at the second indoor expansion valve 38 is evaporated in the second indoor heat exchanger 36, and the evaporated refrigerants are joined. Then, the joined refrigerant flows through the gas-side connection pipe 5, passes through the gas-side shutoff valve 28 and the four-way switching valve 22, is heated in the internal heat exchanger 51, and is sucked by the compressor 21 again.

(3-12-3) Heating Operating Mode

In the air conditioning apparatus 1 k, in the heating operating mode, capacity control is performed on the operating frequency of the compressor 21, for example, such that the condensation temperature of the refrigerant in the refrigerant circuit 10 becomes a target condensation temperature. In this case, the target condensation temperature is preferably determined in accordance with one of the indoor units 30 and 35 having the largest difference between the set temperature and the indoor temperature (an indoor unit having the largest load).

The gas refrigerant discharged from the compressor 21 flows through the four-way switching valve 22 and the gas-side connection pipe 5, and then flows into each of the first indoor unit 30 and the second indoor unit 35.

The refrigerant which has flowed into the first indoor unit 30 is condensed in the first indoor heat exchanger 31. The refrigerant which has flowed into the second indoor unit 35 is condensed in the second indoor heat exchanger 36.

The refrigerant which has flowed out from the liquid-side end of the first indoor heat exchanger 31 is decompressed at the first indoor expansion valve 33 to an intermediate pressure in the refrigeration cycle. The refrigerant which has flowed out from the liquid-side end of the second indoor heat exchanger 36 is also likewise decompressed at the second indoor expansion valve 38 to an intermediate pressure in the refrigeration cycle.

In this case, the valve opening degree of the first indoor expansion valve 33 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the first indoor heat exchanger 31 becomes a target value. Also, the valve opening degree of the second indoor expansion valve 38 is controlled to satisfy a predetermined condition, for example, such that the degree of subcooling of the refrigerant flowing through the liquid-side outlet of the second indoor heat exchanger 36 becomes a target value.

The refrigerant which has passed through the first indoor expansion valve 33 and the refrigerant which has passed through the second indoor expansion valve 38 are joined. Then, the joined refrigerant passes through the liquid-side connection pipe 6 and flows into the outdoor unit 20.

The refrigerant which has flowed into the outdoor unit 20 passes through the liquid-side shutoff valve 29 and is decompressed at the outdoor expansion valve 24 to a low pressure in the refrigeration cycle.

In this case, the valve opening degree of the outdoor expansion valve 24 is controlled to satisfy a predetermined condition, for example, such that the degree of superheating of the refrigerant to be sucked by the compressor 21 becomes a target value. Note that the method of controlling the valve opening degree of the outdoor expansion valve 24 is not limited, and, for example, control may be performed such that the discharge temperature of the refrigerant discharged from the compressor 21 becomes a predetermined temperature, or the degree of superheating of the refrigerant discharged from the compressor 21 satisfies a predetermined condition.

The refrigerant decompressed at the outdoor expansion valve 24 is evaporated in the outdoor heat exchanger 23, passes through the four-way switching valve 22, is heated in the internal heat exchanger 51, and is sucked into the compressor 21 again.

(3-12-4) Characteristics of Twelfth Embodiment

Since the air conditioning apparatus 1 k can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene, the air conditioning apparatus 1 k can perform a refrigeration cycle using a small-GWP refrigerant.

In the air conditioning apparatus 1 k, during heating operation, since subcooling control is performed on the first indoor expansion valve 33 and the second indoor expansion valve 38, the capacities of the first indoor heat exchanger 31 and the second indoor heat exchanger 36 can be likely sufficiently provided.

Furthermore, since the air conditioning apparatus 1 k is provided with the internal heat exchanger 51, the refrigerant to be sucked into the compressor 21 is heated and liquid compression in the compressor 21 is suppressed. Control can be provided to cause the degrees of superheating of the refrigerant flowing through the outlets of the first indoor heat exchanger 31 and the second indoor heat exchanger 36 that function as the evaporators of the refrigerant during cooling operation to be small values. Also, similarly in heating operation, control can be provided to cause the degree of superheating of the refrigerant flowing through the outlet of the outdoor heat exchanger 23 that functions as the evaporator of the refrigerant to be a small value. Thus, in either of cooling operation and heating operation, even when use of a nonazeotropic mixed refrigerant as the refrigerant causes a temperature glide in the evaporator, the capacity of the heat exchanger that functions as the evaporator can be sufficiently provided.

(13) Embodiment of the Technique of Thirteenth Group (13-1) First Embodiment

FIG. 4A is a configuration diagram of an air conditioner 1 according to a first embodiment of the present disclosure. In FIG. 4A, the air conditioner 1 is constituted by a utilization unit 2 and a heat source unit 3.

(13-1-1) Configuration of Air Conditioner 1

The air conditioner 1 has a refrigerant circuit 11 in which a compressor 100, a four-way switching valve 16, a heat-source-side heat exchanger 17, an expansion valve 18 serving as a decompression mechanism, and a utilization-side heat exchanger 13 are connected in a loop shape by refrigerant pipes.

In this embodiment, the refrigerant circuit 11 is filled with refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a refrigerant mixture containing 1,2-difluoroethylene, and any one of the above-described refrigerant A to refrigerant D can be used. The refrigerant circuit 11 is filled with refrigerating machine oil together with the refrigerant mixture.

(13-1-1-1) Utilization Unit 2

In the refrigerant circuit 11, the utilization-side heat exchanger 13 belongs to the utilization unit 2. In addition, a utilization-side fan 14 is mounted in the utilization unit 2. The utilization-side fan 14 generates an air flow to the utilization-side heat exchanger 13.

A utilization-side communicator 35 and a utilization-side microcomputer 41 are mounted in the utilization unit 2. The utilization-side communicator 35 is connected to the utilization-side microcomputer 41.

The utilization-side communicator 35 is used by the utilization unit 2 to communicate with the heat source unit 3. The utilization-side microcomputer 41 is supplied with a control voltage even during a standby state in which the air conditioner 1 is not operating. Thus, the utilization-side microcomputer 41 is constantly activated.

(13-1-1-2) Heat Source Unit 3

In the refrigerant circuit 11, the compressor 100, the four-way switching valve 16, the heat-source-side heat exchanger 17, and the expansion valve 18 belong to the heat source unit 3. In addition, a heat-source-side fan 19 is mounted in the heat source unit 3. The heat-source-side fan 19 generates an air flow to the heat-source-side heat exchanger 17.

In addition, a power conversion device 30, a heat-source-side communicator 36, and a heat-source-side microcomputer 42 are mounted in the heat source unit 3. The power conversion device 30 and the heat-source-side communicator 36 are connected to the heat-source-side microcomputer 42.

The power conversion device 30 is a circuit for driving a motor 70 of the compressor 100. The heat-source-side communicator 36 is used by the heat source unit 3 to communicate with the utilization unit 2. The heat-source-side microcomputer 42 controls the motor 70 of the compressor 100 via the power conversion device 30 and also controls other devices in the heat source unit 3 (for example, the heat-source-side fan 19).

FIG. 4B is a circuit block diagram of the power conversion device 30. In FIG. 4B, the motor 70 of the compressor 100 is a three-phase brushless DC motor and includes a stator 72 and a rotor 71. The stator 72 includes star-connected phase windings Lu, Lv, and Lw of a U-phase, a V-phase, and a W-phase. One ends of the phase windings Lu, Lv, and Lw are respectively connected to phase winding terminals TU. TV, and TW of wiring lines of the U-phase, the V-phase, and the W-phase extending from an inverter 25. The other ends of the phase windings Lu, Lv, and Lw are connected to each other at a terminal TN. These phase windings Lu. Lv, and Lw each generate an induced voltage in accordance with the rotation speed and position of the rotor 71 when the rotor 71 rotates.

The rotor 71 includes a permanent magnet with a plurality of poles, the N-pole and the S-pole, and rotates about a rotation axis with respect to the stator 72.

(13-1-2) Configuration of Power Conversion Device 30

The power conversion device 30 is mounted in the heat source unit 3, as illustrated in FIG. 4A. The power conversion device 30 is constituted by a power source circuit 20, the inverter 25, a gate driving circuit 26, and the heat-source-side microcomputer 42, as illustrated in FIG. 4B. The power source circuit 20 is constituted by a rectifier circuit 21 and a capacitor 22.

(13-1-2-1) Rectifier Circuit 21

The rectifier circuit 21 has a bridge structure made up of four diodes D1 a, D1 b, D2 a, and D2 b. Specifically, the diodes D1 a and D1 b are connected in series to each other, and the diodes D2 a and D2 b are connected in series to each other. The cathode terminals of the diodes D1 a and D2 a are connected to a plus-side terminal of the capacitor 22 and function as a positive-side output terminal of the rectifier circuit 21. The anode terminals of the diodes D1 b and D2 b are connected to a minus-side terminal of the capacitor 22 and function as a negative-side output terminal of the rectifier circuit 21.

A node between the diode D1 a and the diode D1 b is connected to one pole of an alternating-current (AC) power source 90. Anode between the diode D2 a and the diode D2 b is connected to the other pole of the AC power source 90. The rectifier circuit 21 rectifies an AC voltage output from the AC power source 90 to generate a direct-current (DC) voltage, and supplies the DC voltage to the capacitor 22.

(13-1-2-2) Capacitor 22

The capacitor 22 has one end connected to the positive-side output terminal of the rectifier circuit 21 and has the other end connected to the negative-side output terminal of the rectifier circuit 21. The capacitor 22 is a small-capacitance capacitor that does not have a large capacitance for smoothing a voltage rectified by the rectifier circuit 21. Hereinafter, a voltage between the terminals of the capacitor 22 will be referred to as a DC bus voltage Vdc for the convenience of description.

The DC bus voltage Vdc is applied to the inverter 25 connected to the output side of the capacitor 22. In other words, the rectifier circuit 21 and the capacitor 22 constitute the power source circuit 20 for the inverter 25.

The capacitor 22 smooths voltage variation caused by switching in the inverter 25. In this embodiment, a film capacitor is adopted as the capacitor 22.

(13-1-2-3) Voltage Detector 23

A voltage detector 23 is connected to the output side of the capacitor 22 and is for detecting the value of a voltage across the capacitor 22, that is, the DC bus voltage Vdc. The voltage detector 23 is configured such that, for example, two resistors connected in series to each other are connected in parallel to the capacitor 22 and the DC bus voltage Vdc is divided. A voltage value at a node between the two resistors is input to the heat-source-side microcomputer 42.

(13-1-2-4) Current Detector 24

A current detector 24 is connected between the capacitor 22 and the inverter 25 and to the negative-side output terminal side of the capacitor 22. The current detector 24 detects a motor current that flows through the motor 70 after the motor 70 is activated, as a total value of currents of the three phases.

The current detector 24 may be constituted by, for example, an amplifier circuit including a shunt resistor and an operational amplifier that amplifies a voltage across the shunt resistor. The motor current detected by the current detector 24 is input to the heat-source-side microcomputer 42.

(13-1-2-5) Inverter 25

In the inverter 25, three pairs of upper and lower arms respectively corresponding to the phase windings Lu, Lv, and Lw of the U-phase, the V-phase, and the W-phase of the motor 70 are connected in parallel to each other and connected to the output side of the capacitor 22.

In FIG. 4B, the inverter 25 includes a plurality of insulated gate bipolar transistors (IGBTs, hereinafter simply referred to as transistors) Q3 a, Q3 b, Q4 a, Q4 b, Q5 a, and Q5 b, and a plurality of free wheeling diodes D3 a, D3 b, D4 a, D4 b, D5 a, and D5 b.

The transistors Q3 a and Q3 b are connected in series to each other, the transistors Q4 a and Q4 b are connected in series to each other, and the transistors Q5 a and Q5 b are connected in series to each other, to constitute respective upper and lower arms and to form nodes NU, NV, and NW, from which output lines extend toward the phase windings Lu, Lv, and Lw of the corresponding phases.

The diodes D3 a to D5 b are connected in parallel to the respective transistors Q3 a to Q5 b such that the collector terminal of the transistor is connected to the cathode terminal of the diode and that the emitter terminal of the transistor is connected to the anode terminal of the diode. The transistor and the diode connected in parallel to each other constitute a switching element.

The inverter 25 generates driving voltages SU, SV, and SW for driving the motor 70 in response to ON and OFF of the transistors Q3 a to Q5 b at the timing when the DC bus voltage Vdc is applied from the capacitor 22 and when an instruction is provided from the gate driving circuit 26. The driving voltages SU, SV, and SW are respectively output from the node NU between the transistors Q3 a and Q3 b, the node NV between the transistors Q4 a and Q4 b, and the node NW between the transistors Q5 a and Q5 b to the phase windings Lu, Lv, and Lw of the motor 70.

(13-1-2-6) Gate Driving Circuit 26

The gate driving circuit 26 changes the ON and OFF states of the transistors Q3 a to Q5 b of the inverter 25 on the basis of instruction voltages from the heat-source-side microcomputer 42. Specifically, the gate driving circuit 26 generates gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be applied to the gates of the respective transistors Q3 a to Q5 b so that the pulsed driving voltages SU, SV, and SW having a duty determined by the heat-source-side microcomputer 42 are output from the inverter 25 to the motor 70. The generated gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz are applied to the gate terminals of the respective transistors Q3 a to Q5 b.

(13-1-2-7) Heat-Source-Side Microcomputer 42

The heat-source-side microcomputer 42 is connected to the voltage detector 23, the current detector 24, and the gate driving circuit 26. In this embodiment, the heat-source-side microcomputer 42 causes the motor 70 to be driven by using a rotor position sensorless method. The driving method is not limited to the rotor position sensorless method, and a sensor method may be used.

The rotor position sensorless method is a method for performing driving by estimating the position and rotation rate of the rotor, performing PI control on the rotation rate, performing PI control on a motor current, and the like, by using various parameters indicating the characteristics of the motor 70, a detection result of the voltage detector 23 after the motor 70 is activated, a detection result of the current detector 24, and a predetermined formula model about control of the motor 70, and the like. The various parameters indicating the characteristics of the motor 70 include a winding resistance, an inductance component, an induced voltage, and the number of poles of the motor 70 that is used. For details of rotor position sensorless control, see patent literatures (for example, Japanese Unexamined Patent Application Publication No. 2013-17289).

(13-1-3) Features of First Embodiment

(13-1-3-1)

In the air conditioner 1 that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the rotation rate of the motor 70 can be changed via the power conversion device 30 as necessary. In other words, the motor rotation rate of the compressor 100 can be changed in accordance with an air conditioning load, and thus a high annual performance factor (APF) can be achieved.

(13-1-3-2)

An electrolytic capacitor is not required on the output side of the rectifier circuit 21, and thus an increase in the size and cost of the circuit is suppressed.

(13-1-4) Modification Example of First Embodiment

FIG. 4C is a circuit block diagram of a power conversion device 130 according to a modification example of the first embodiment. In FIG. 4C, this modification example is different from the first embodiment in that a rectifier circuit 121 for three phases is adopted instead of the rectifier circuit 21 for a single phase, to support a three-phase AC power source 190 instead of the single-phase AC power source 90.

The rectifier circuit 121 has a bridge structure made up of six diodes D0 a, D0 b, D1 a. D1 b, D2 a, and D2 b. Specifically, the diodes D0 a and D0 b are connected in series to each other, the diodes D1 a and D1 b are connected in series to each other, and the diodes D2 a and D2 b are connected in series to each other.

The cathode terminals of the diodes D0 a, D1 a, and D2 a are connected to the plus-side terminal of the capacitor 22 and function as a positive-side output terminal of the rectifier circuit 121. The anode terminals of the diodes D0 b, D1 b, and D2 b are connected to the minus-side terminal of the capacitor 22 and function as a negative-side output terminal of the rectifier circuit 121.

A node between the diode D0 a and the diode D0 b is connected to an R-phase output side of the AC power source 190. A node between the diode D1 a and the diode D1 b is connected to an S-phase output side of the AC power source 190. A node between the diode D2 a and the diode D2 b is connected to a T-phase output side of the AC power source 190. The rectifier circuit 121 rectifies an AC voltage output from the AC power source 190 to generate a DC voltage, and supplies the DC voltage to the capacitor 22.

Other than that, the configuration is similar to that of the above-described embodiment, and thus the description thereof is omitted.

(13-1-5) Features of Modification Example of First Embodiment

(13-1-5-1)

In the air conditioner 1 that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the rotation rate of the motor 70 can be changed via the power conversion device 130 as necessary. In other words, the motor rotation rate of the compressor 100 can be changed in accordance with an air conditioning load, and thus a high annual performance factor (APF) can be achieved.

(13-1-5-2)

An electrolytic capacitor is not required on the output side of the rectifier circuit 121, and thus an increase in the size and cost of the circuit is suppressed.

(13-2) Second Embodiment

FIG. 4D is a circuit block diagram of a power conversion device 30B mounted in an air conditioner according to a second embodiment of the present disclosure.

(13-2-1) Configuration of Power Conversion Device 30B

In FIG. 4D, the power conversion device 30B is an indirect matrix converter. The difference from the power conversion device 30 according to the first embodiment in FIG. 4B is that a converter 27 is adopted instead of the rectifier circuit 21 and that a gate driving circuit 28 and a reactor 33 are newly added. Other than that, the configuration is similar to that of the first embodiment.

Here, a description will be given of the converter 27, the gate driving circuit 28, and the reactor 33, and a description of the other components is omitted.

(13-2-1-1) Converter 27

In FIG. 4D, the converter 27 includes a plurality of insulated gate bipolar transistors (IGBTs, hereinafter simply referred to as transistors) Q1 a, Q1 b, Q2 a, and Q2 b, and a plurality of diodes D1 a, D1 b, D2 a, and D2 b.

The transistors Q1 a and Q1 b are connected in series to each other to constitute upper and lower arms, and a node formed accordingly is connected to one pole of the AC power source 90. The transistors Q2 a and Q2 b are connected in series to each other to constitute upper and lower arms, and a node formed accordingly is connected to the other pole of the AC power source 90.

The diodes D1 a to D2 b are connected in parallel to the respective transistors Q1 a to Q2 b such that the collector terminal of the transistor is connected to the cathode terminal of the diode and that the emitter terminal of the transistor is connected to the anode terminal of the diode. The transistor and the diode connected in parallel to each other constitute a switching element.

In the converter 27, the transistors Q1 a to Q2 b are turned ON and OFF at the timing when an instruction is provided from the gate driving circuit 28.

(13-2-1-2) Gate Driving Circuit 28

The gate driving circuit 28 changes the ON and OFF states of the transistors Q1 a to Q2 b of the converter 27 on the basis of instruction voltages from the heat-source-side microcomputer 42. Specifically, the gate driving circuit 28 generates pulsed gate control voltages Pq, Pr, Ps, and Pt having a duty determined by the heat-source-side microcomputer 42 so as to control a current flowing from the AC power source 90 toward the heat source to a predetermined value. The generated gate control voltages Pq, Pr, Ps, and Pt are applied to the gate terminals of the respective transistors Q1 a to Q2 b.

(13-2-1-3) Reactor 33

The reactor 33 is connected in series to the AC power source 90 between the AC power source 90 and the converter 27. Specifically, one end thereof is connected to one pole of the AC power source 90, and the other end thereof is connected to one input terminal of the converter 27.

(13-2-2) Operation

The heat-source-side microcomputer 42 turns ON/OFF the transistors Q1 a and Q1 b or the transistors Q2 a and Q2 b of the upper and lower arms of the converter 27 to short-circuit/open the transistors for a predetermined time, and controls a current to, for example, a substantially sinusoidal state, thereby improving a power factor of power source input and suppressing harmonic components.

In addition, the heat-source-side microcomputer 42 performs cooperative control between the converter and the inverter so as to control a short-circuit period on the basis of a duty ratio of a gate control voltage for controlling the inverter 25.

(13-2-3) Features of Second Embodiment

The air conditioner 1 is highly efficient and does not require an electrolytic capacitor on the output side of the converter 27, and thus an increase in the size and cost of the circuit is suppressed.

(13-2-4) Configuration of Power Conversion Device 130B According to Modification Example of Second Embodiment

FIG. 4E is a circuit block diagram of a power conversion device 130B according to a modification example of the second embodiment. In FIG. 4E, this modification example is different from the second embodiment in that a converter 127 for three phases is adopted instead of the converter 27 for a single phase, to support the three-phase AC power source 190 instead of the single-phase AC power source 90. In accordance with the change from the converter 27 for a single phase to the converter 127 for three phases, a gate driving circuit 128 is adopted instead of the gate driving circuit 28. Furthermore, reactors 33 are connected between the converter 127 and the output sides of the respective phases. Capacitors are connected between input-side terminals of the reactors 33. Alternatively, these capacitors may be removed.

(13-2-4-1) Converter 127

The converter 127 includes a plurality of insulated gate bipolar transistors (IGBTs, hereinafter simply referred to as transistors) Q0 a, Q0 b, Q1 a, Q1 b, Q2 a, and Q2 b, and a plurality of diodes D0 a, D0 b, D1 a, D1 b, D2 a, and D2 b.

The transistors Q0 a and Q0 b are connected in series to each other to constitute upper and lower arms, and a node formed accordingly is connected to the R-phase output side of the AC power source 190. The transistors Q1 a and Q1 b are connected in series to each other to constitute upper and lower arms, and a node formed accordingly is connected to the S-phase output side of the AC power source 190. The transistors Q2 a and Q2 b are connected in series to each other to constitute upper and lower arms, and a node formed accordingly is connected to the T-phase output side of the AC power source 190.

The diodes D0 a to D2 b are connected in parallel to the respective transistors Q0 a to Q2 b such that the collector terminal of the transistor is connected to the cathode terminal of the diode and that the emitter terminal of the transistor is connected to the anode terminal of the diode. The transistor and the diode connected in parallel to each other constitute a switching element.

In the converter 127, the transistors Q0 a to Q2 b are turned ON and OFF at the timing when an instruction is provided from the gate driving circuit 128.

(13-2-4-2) Gate Driving Circuit 128

The gate driving circuit 128 changes the ON and OFF states of the transistors Q0 a to Q2 b of the converter 127 on the basis of instruction voltages from the heat-source-side microcomputer 42. Specifically, the gate driving circuit 128 generates pulsed gate control voltages Po, Pp, Pq, Pr, Ps, and Pt having a duty determined by the heat-source-side microcomputer 42 so as to control a current flowing from the AC power source 190 toward the heat source to a predetermined value. The generated gate control voltages Po, Pp, Pq, Pr, Ps, and Pt are applied to the gate terminals of the respective transistors Q0 a to Q2 b.

(13-2-5) Features of Modification Example of Second Embodiment

The air conditioner 1 is highly efficient and does not require an electrolytic capacitor on the output side of the converter 127, and thus an increase in the size and cost of the circuit is suppressed.

(13-3) Third Embodiment

FIG. 4F is a circuit block diagram of a power conversion device 30C mounted in an air conditioner according to a third embodiment of the present disclosure.

(13-3-1) Configuration of Power Conversion Device 30C According to Third Embodiment

In FIG. 4F, the power conversion device 30C is a matrix converter 29.

(13-3-1-1) Configuration of Matrix Converter 29

The matrix converter 29 is configured by connecting bidirectional switches S1 a, S2 a, and S3 a to one end of input from the AC power source 90 and connecting bidirectional switches S1 b, S2 b, and S3 b to the other end.

An intermediate terminal between the bidirectional switch S1 a and the bidirectional switch Sib connected in series to each other is connected to one end of the U-phase winding Lu among the three-phase windings of the motor 70. An intermediate terminal between the bidirectional switch S2 a and the bidirectional switch S2 b connected in series to each other is connected to one end of the V-phase winding Lv among the three-phase windings of the motor 70. An intermediate terminal between the bidirectional switch S3 and the bidirectional switch S3 b connected in series to each other is connected to one end of the W-phase winding Lw among the three-phase windings of the motor 70.

AC power input from the AC power source 90 is switched by the bidirectional switches S1 a to S3 b and is converted into AC having a predetermined frequency, thereby being capable of driving the motor 70.

(13-3-1-2) Configuration of Bidirectional Switch

FIG. 4G is a circuit diagram conceptionally illustrating a bidirectional switch. In FIG. 4G, the bidirectional switch includes transistors Q61 and Q62, diodes D61 and D62, and terminals Ta and Tb. The transistors Q61 and Q62 are insulated gate bipolar transistors (IGBTs).

The transistor Q61 has an emitter E connected to the terminal Ta, and a collector C connected to the terminal Tb via the diode D61. The collector C is connected to the cathode of the diode D61.

The transistor Q62 has an emitter E connected to the terminal Tb, and a collector C connected to the terminal Ta via the diode D62. The collector C is connected to the cathode of the diode D62. The terminal Ta is connected to an input side, and the terminal Tb is connected to an output side.

Turning ON of the transistor Q61 and turning OFF of the transistor Q62 enables a current to flow from the terminal Tb to the terminal Ta via the diode D61 and the transistor Q61 in this order. At this time, a flow of a current from the terminal Ta to the terminal Tb (backflow) is prevented by the diode D61.

On the other hand, turning OFF of the transistor Q61 and turning ON of the transistor Q62 enables a current to flow from the terminal Ta to the terminal Tb via the diode D62 and the transistor Q62 in this order. At this time, a flow of a current from the terminal Tb to the terminal Ta (backflow) is prevented by the diode D62.

(13-3-2) Operation

FIG. 4H is a circuit diagram illustrating an example of a current direction in the matrix converter 29. FIG. 4H illustrates an example of a path of a current that flows from the AC power source 90 via the matrix converter 29 to the motor 70. The current flows from one pole of the AC power source 90 to the other pole of the AC power source 90 via the bidirectional switch S1 a, the U-phase winding Lu which is one of the three-phase windings of the motor 70, the W-phase winding Lw, and the bidirectional switch S3 b. Accordingly, power is supplied to the motor 70 and the motor 70 is driven.

FIG. 4I is a circuit diagram illustrating an example of another current direction in the matrix converter 29. In FIG. 4I, a current flows from one pole of the AC power source 90 to the other pole of the AC power source 90 via the bidirectional switch S3 a, the W-phase winding Lw which is one of the three-phase windings of the motor 70, the U-phase winding Lu, and the bidirectional switch S1 b. Accordingly, power is supplied to the motor 70 and the motor 70 is driven.

(13-3-3) Features of Third Embodiment

The air conditioner 1 is highly efficient and does not require an electrolytic capacitor on the output side of the matrix converter 29, and thus an increase in the size and cost of the circuit is suppressed.

(13-3-4) Configuration of Power Conversion Device 130C According to Modification Example of Third Embodiment

FIG. 4Q is a circuit block diagram of a power conversion device 130C according to a modification example of the third embodiment. In FIG. 4J, this modification example is different from the third embodiment in that a matrix converter 129 for three phases is adopted instead of the matrix converter 29 for a single phase, to support the three-phase AC power source 190 instead of the single-phase AC power source 90.

(13-3-4-1) Configuration of Matrix Converter 129

It is also a difference that a gate driving circuit 131 is adopted instead of a gate driving circuit 31 in accordance with the change from the matrix converter 29 for a single phase to the matrix converter 129 for three phases. Furthermore, reactors L1, L2, and L3 are connected between the matrix converter 129 and the output sides of the respective phases.

Predetermined three-phase AC voltages obtained through conversion by bidirectional switches S1 a to S3 c are supplied to the motor 70 via the phase winding terminals TU, TV, and TW. The reactors L1, L2, and L3 are connected to respective input terminals of matrix converter 129. Capacitors C1, C2, and C3 are connected to each other at one ends thereof, and the other ends thereof are connected to output terminals of matrix converter 129.

In the power conversion device 130C, the reactors L1, L2, and L3 are short-circuited via the matrix converter 129, and thereby the energy supplied from the three-phase AC power source 190 can be accumulated in the reactors L1, L2, and L3 and the voltages across the capacitors C1, C2, and C3 can be increased. Accordingly, a voltage utilization rate of 1 or more can be achieved.

At this time, voltage-type three-phase AC voltages Vr, Vs, and Vt are input to the input terminals of the matrix converter 129, and current-type three-phase AC voltages Vu, Vv, and Vw are output from the output terminals.

In addition, the capacitors C1, C2, and C3 constitute LC filters with the reactors L1, L2, and L3, respectively. Thus, high-frequency components included in voltages output to the output terminals can be reduced, and torque pulsation components and noise generated in the motor 70 can be reduced.

Furthermore, compared with an AC-AC conversion circuit including a rectifier circuit and an inverter, the number of switching elements is smaller, and the loss that occurs in the power conversion device 130C can be reduced.

(13-3-4-2) Configuration of Clamp Circuit 133

In the power conversion device 130, a clamp circuit 133 is connected between the input terminals and the output terminals. Thus, a surge voltage generated between the input terminals and the output terminals of the matrix converter 129 through switching of the bidirectional switches S1 a to S3 c can be absorbed by a capacitor in the clamp circuit 133 (see FIG. 4I).

FIG. 4K is a circuit diagram of the clamp circuit 133. In FIG. 4K, the clamp circuit 133 has diodes D31 a to D36 b, a capacitor C37, and terminals 135 to 140.

The anode of the diode D31 a and the cathode of the diode D31 b are connected to the terminal 135. The anode of the diode D32 a and the cathode of the diode D32 b are connected to the terminal 136. The anode of the diode D33 a and the cathode of the diode D33 b are connected to the terminal 137.

The cathodes of the diodes D31 a, D32 a, and D33 a are connected to one end of the capacitor C37. The anodes of the diodes D31 b, D32 b, and D33 b are connected to the other end of the capacitor C37.

The anode of the diode D34 a and the cathode of the diode D34 b are connected to the terminal 138. The anode of the diode D35 a and the cathode of the diode D35 b are connected to the terminal 139. The anode of the diode D36 a and the cathode of the diode D36 b are connected to the terminal 140.

The cathodes of the diodes D34 a. D35 a, and D36 a are connected to the one end of the capacitor C37. The anodes of the diodes D34 b, D35 b, and D36 b are connected to the other end of the capacitor C37.

The terminals 135, 136, and 137 are connected to the input side of the matrix converter 129, and the terminals 138, 139, and 140 are connected to the output side of the matrix converter 129. Because the clamp circuit 133 is connected between the input terminals and the output terminals, a surge voltage generated between the input terminals and the output terminals of the matrix converter 129 through switching of the bidirectional switches S1 a to S3 b can be absorbed by the capacitor C37 in the clamp circuit 133.

As described above, the power conversion device 130C is capable of supplying a voltage larger than a power source voltage to the motor 70. Thus, even if the current flowing through the power conversion device 130C and the motor 70 is small, a predetermined motor output can be obtained, in other words, only a small current is used. Accordingly, the loss that occurs in the power conversion device 130C and the motor 70 can be reduced.

(13-3-5) Features of Modification Example of Third Embodiment

The air conditioner 1 is highly efficient and does not require an electrolytic capacitor on the output side of the matrix converter 129, and thus an increase in the size and cost of the circuit is suppressed.

(13-4) Others 13-4-1

As the compressor 100 of the air conditioner 1, any one of a scroll compressor, a rotary compressor, a turbo compressor, and a screw compressor is adopted.

13-4-2

The motor 70 of the compressor 100 is a permanent magnet synchronous motor having the rotor 71 including a permanent magnet.

(14) Embodiment of the Technique of Fourteenth Group (14-1) Specific Embodiment

FIG. 5A is a configuration diagram of an air conditioner 1 according to a first embodiment of the present disclosure. In FIG. 5A, the air conditioner 1 is constituted by a utilization unit 2 and a heat source unit 3.

(14-1-1) Configuration of Air Conditioner 1

The air conditioner 1 has a refrigerant circuit 11 in which a compressor 100, a four-way switching valve 16, a heat-source-side heat exchanger 17, an expansion valve 18 serving as a decompression mechanism, and a utilization-side heat exchanger 13 are connected in a loop shape by refrigerant pipes.

In this embodiment, the refrigerant circuit 11 is filled with refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a refrigerant mixture containing 1,2-difluoroethylene, and any one of the above-described refrigerant A to refrigerant D can be used. The refrigerant circuit 11 is filled with refrigerating machine oil together with the refrigerant mixture.

(14-1-1-1) Utilization Unit 2

In the refrigerant circuit 11, the utilization-side heat exchanger 13 belongs to the utilization unit 2. In addition, a utilization-side fan 14 is mounted in the utilization unit 2. The utilization-side fan 14 generates an air flow to the utilization-side heat exchanger 13.

A utilization-side communicator 35 and a utilization-side microcomputer 41 are mounted in the utilization unit 2. The utilization-side communicator 35 is connected to the utilization-side microcomputer 41.

The utilization-side communicator 35 is used by the utilization unit 2 to communicate with the heat source unit 3. The utilization-side microcomputer 41 is supplied with a control voltage even during a standby state in which the air conditioner 1 is not operating. Thus, the utilization-side microcomputer 41 is constantly activated.

(14-1-1-2) Heat Source Unit 3

In the refrigerant circuit 11, the compressor 100, the four-way switching valve 16, the heat-source-side heat exchanger 17, and the expansion valve 18 belong to the heat source unit 3. In addition, a heat-source-side fan 19 is mounted in the heat source unit 3. The heat-source-side fan 19 generates an air flow to the heat-source-side heat exchanger 17.

In addition, a connection unit 30, a heat-source-side communicator 36, and a heat-source-side microcomputer 42 are mounted in the heat source unit 3. The connection unit 30 and the heat-source-side communicator 36 are connected to the heat-source-side microcomputer 42.

(14-1-2) Configuration of Connection Unit 30

FIG. 5B is an operation circuit diagram of a motor 70 of the compressor 100. In FIG. 5B, the connection unit 30 is a circuit that causes power to be supplied from an alternating-current (AC) power source 90 to the motor 70 of the compressor 100 without frequency conversion.

The motor 70 is an induction motor and includes a squirrel-cage rotor 71, and a stator 72 having a main winding 727 and an auxiliary winding 728. The squirrel-cage rotor 71 rotates following a rotating magnetic field generated by the stator 72.

The compressor 100 has an M terminal, an S terminal, and a C terminal. The M terminal and the C terminal are connected by the main winding 727. The S terminal and the C terminal are connected by the auxiliary winding 728.

The AC power source 90 and the compressor 100 are connected by power supply lines 901 and 902 that supply an AC voltage to the compressor 100. The power supply line 901 is connected to the C terminal via a thermostat 26.

The thermostat 26 detects a temperature of a room equipped with the air conditioner 1. The thermostat 26 opens the contact thereof when the room temperature is within a set temperature range and closes the contact when the room temperature is out of the set temperature range.

The power supply line 902 branches off into a first branch line 902A and a second branch line 902B. The first branch line 902A is connected to the M terminal, and the second branch line 902B is connected to the S terminal via an activation circuit 20.

The activation circuit 20 is a circuit in which a positive temperature coefficient (PTC) thermistor 21 and an operation capacitor 22 are connected in parallel to each other.

In this embodiment, the thermostat 26 connected to the power supply line 901 and the activation circuit 20 connected to the power supply line 902 are referred to as the connection unit 30.

(14-1-3) Operation

In the operation circuit of the compressor 100 having the above-described configuration, turning on of the AC power source 90 causes a current to flow through the auxiliary winding 728 via the PTC thermistor 21 and the motor 70 to be activated.

After the motor 70 has been activated, the PTC thermistor 21 self-heats by using the current flowing therethrough, and the resistance value thereof increases. As a result, the operation capacitor 22, instead of the PTC thermistor 21, is connected to the auxiliary winding 728, and the state shifts to a stable operation state.

(14-1-4) Features

(14-1-4-1)

In the air conditioner 1 that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the compressor 100 can be driven without interposing a power conversion device between the AC power source 90 and the motor 70. Thus, it is possible to provide the air conditioner 1 that is environmentally friendly and has a relatively inexpensive configuration.

(14-1-4-2)

In the air conditioner 1 that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the connection between the auxiliary winding 728 and the activation circuit 20, which is a parallel circuit of the PTC thermistor 21 and the operation capacitor 22, makes it possible to achieve a large activation torque of the motor 70 of the compressor 100.

After the compressor 100 has been activated, the PTC thermistor 21 self-heats and the resistance value thereof increases, the state changes to a state where the operation capacitor 22 and the auxiliary winding 728 are substantially connected to each other, and the compressor 100 is operated at a constant rotation rate (power source frequency). Thus, the compressor 100 enters a state of being capable of outputting a rated torque. As described above, in the air conditioner 1, switching of connection to the operation capacitor 22 is performed at appropriate timing, and thus the efficiency of the compressor 100 can be increased.

(14-1-4-3)

The motor 70 is an induction motor and is capable of high output with relatively low cost, and thus the efficiency of the air conditioner 1 can be increased.

(14-1-5) Modification Example

FIG. 5C is an operation circuit diagram of a motor 170 of a compressor 200 in the air conditioner 1 according to a modification example. In FIG. 5C, the motor 170 is a three-phase induction motor and is connected to a three-phase AC power source 190 via a connection unit 130.

The connection unit 130 is a relay having contacts 130 u, 130 v, and 130 w. The contact 130 u opens or closes a power supply line 903 between an R terminal of the three-phase AC power source 190 and a U-phase winding Lu of the motor 170. The contact 130 v opens or closes a power supply line 904 between an S terminal of the three-phase AC power source 190 and a V-phase winding Lv of the motor 170. The contact 130 w opens or closes a power supply line 905 between a T terminal of the three-phase AC power source 190 and a W-phase winding Lw of the motor 170.

AC voltages are supplied from the R terminal, the S terminal, and the T terminal of the three-phase AC power source 190 to the corresponding U-phase winding Lu, the V-phase winding Lv, and the W-phase winding Lw of the motor 170. The AC voltage supplied to the V-phase winding Lv of the motor 170 has a phase difference of 120 degrees with respect to the AC voltage supplied to the U-phase winding Lu. Also, the AC voltage supplied to the W-phase winding Lw of the motor 170 has a phase difference of 120 degrees with respect to the AC voltage supplied to the V-phase winding Lv.

Thus, only the supply of AC voltages from the three-phase AC power source 190 to the motor 170 causes a rotating magnetic field to be generated in the stator 172, and the rotor 171 rotates following the rotating magnetic field. As a result, the compressor 200 is operated at a constant rotation rate (power source frequency). Thus, the operation circuit of the motor 170 does not require the activation circuit 20 according to the foregoing embodiment, and only a relay circuit of the connection unit 130 is used.

(14-1-6) Features of Modification Example

(14-1-6-1)

In the air conditioner 1 that uses a refrigerant mixture containing at least 1,2-difluoroethylene, the compressor 200 can be driven without interposing a power conversion device between the three-phase AC power source 190 and the motor 170. Thus, it is possible to provide the air conditioner 1 that is environmentally friendly and has a relatively inexpensive configuration.

(14-1-6-2)

The motor 170 is an induction motor and is capable of high output with relatively low cost, and thus the efficiency of the air conditioner 1 can be increased.

(15) Embodiment of the Technique of Fifteenth Group (15-1) First Embodiment

As illustrated in FIGS. 6A to 6C, a warm-water supply system 1 that is a warm-water generating apparatus according to a first embodiment includes a heat pump 2, a warm-water storage unit 3, a controller 50 that manages and controls the above-listed components, a remote controller 90 that displays information to a user and that receives an operation by the user, and so forth.

(15-1-1) Heat Pump

The heat pump 2 is a unit that functions as a heat source device for heating water, and includes a refrigerant circuit 20 in which a refrigerant circulates, a fan 24F, various sensors, and so forth. In the present embodiment, the refrigerant circuit 20 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and can use any one of the above-described refrigerants A to D.

The refrigerant circuit 20 is constituted of a compressor 21, a use-side water heat exchanger 22, an electric expansion valve 23, a heat-source-side air heat exchanger 24, a refrigerant pipe 25, and so forth.

The compressor 21 is an inverter output-variable electric compressor.

The water heat exchanger 22 functions as a use-side heat exchanger that uses heat of the refrigerant, and includes a refrigerant pipe 22 r and a water pipe 32 w. The water heat exchanger 22 causes a high-temperature high-pressure gas refrigerant flowing through the refrigerant pipe 22 r after discharged by the compressor 21 of the heat pump 2 and circulating water flowing from the warm-water storage unit 3 (described later) and then flowing through the water pipe 32 w. By the heat exchange in the water heat exchanger 22, the refrigerant passing through the refrigerant pipe 22 r is cooled, and simultaneously the water passing through the water pipe 32 w is heated and heated water (high-temperature water=warm water) is generated.

The electric expansion valve 23 expands a low-temperature high-pressure refrigerant which has exited from the compressor 21 and been cooled through the heat exchange with the water.

The air heat exchanger 24 functions as a heat-source-side heat exchanger that takes heat from the outside air, and causes a low-temperature low-pressure refrigerant in a two-phase state expanded at the electric expansion valve 23 and the outside air to exchange heat with each other. The refrigerant which has absorbed heat from the outside air is evaporated and turns into a low-pressure gas refrigerant, and is sucked by the compressor 21.

The refrigerant pipe 25 connects respective devices in the order of the discharge port of the compressor 21, the refrigerant pipe 22 r in the water heat exchanger 22, the electric expansion valve 23, the air heat exchanger 24, and the suction port of the compressor 21.

The various sensors include, for example, sensors that detect the temperature and pressure relating to the refrigerant. FIG. 6B illustrates, among the sensors, a heat-exchanger inlet water temperature sensor 31T and a heat-exchanger outlet water temperature sensor 32T. The heat-exchanger inlet water temperature sensor 31T detects the temperature of water before entering the water heat exchanger 22. That is, the heat-exchanger inlet water temperature sensor 31T detects the temperature of water before passing through the water heat exchanger 22. The heat-exchanger outlet water temperature sensor 32T detects the temperature of water after passing through the water heat exchanger 22.

(15-1-2) Warm-Water Storage Unit

The warm-water storage unit 3 is a unit that sends water supplied from the outside, such as city water (tap water) to the heat pump 2 so that the heat pump 2 heats the water, and stores the water (heated water) returned from the heat pump 2. Moreover, the warm-water storage unit 3 has a function of sending the heated water of which the temperature has been adjusted by a combustion heating device 4 and a mixing valve 77 to a warm-water supply section 82 so that heated water at a temperature set by the user is supplied.

The warm-water storage unit 3 includes a water intake section 81, the warm-water supply section 82, a warm-water supply tank 35, a circulating water pipe 30, a water-intake warm-water supply pipe 70, the combustion heating device 4, and so forth.

(15-1-2-1) Water Intake Section and Warm-Water Supply Section

The water intake section 81 has a connecting port to which a city-water (tap-water) supply pipe 89 a is connected.

The warm-water supply section 82 has a connecting port to which an in-building pipe 99 a for water supply and warm-water supply extending from a faucet 99 or the like in a building of an installation target is connected.

(15-1-2-2) Warm-Water Storage Tank

The warm-water storage tank 35 is a tank in which water heated by the heat pump 2 (heated water) is stored in advance before the user turns the faucet 99 for use. The warm-water storage tank 35 is usually filled with water. The warm-water storage tank 35 is provided with a tank-temperature-distribution detection sensor to cause the controller 50 to recognize the amount of water at a predetermined temperature or higher, in this case, a high temperature of 70° C. or higher (hereinafter, referred to as high-temperature water). The tank-temperature-distribution detection sensor is constituted of six sensors of a first sensor T1, a second sensor T2, a third sensor T3, a fourth sensor T4, a fifth sensor T5, and a sixth sensor T6 in that order from a lower portion toward an upper portion of the warm-water storage tank 35. The controller 50 drives the heat pump 2 to perform a boiling operation based on water temperatures at respective height positions in the warm-water storage tank 35 detected by the tank-temperature-distribution detection sensors T1 to T6 and setting with the remote controller 90. The boiling operation is an operation to increase the heat quantity of water until the temperature of water in the warm-water storage tank 35 reaches a target temperature. The target temperature in the boiling operation, that is, a target warm-water storage temperature of the water in the warm-water storage tank 35 is, for example, set in advance in a manufacturing plant of the warm-water supply system 1. In the present embodiment, the target warm-water storage temperature is 75° C.

If the temperature detection value of the sixth sensor T6 is lower than 70° C., the residual warm water amount is 0. If the temperature detection value of the sixth sensor T6 is 70° C. or higher, the residual warm water amount is 1. Furthermore, if the temperature detection value of the fifth sensor T5 is also 70° C. or higher, the residual warm water amount is 2. Likewise, the levels of the residual warm water amount includes 3, 4, 5, and 6. The residual warm water amount is 6 at maximum if the temperature detection value of the first sensor T1 is also 70° C. or higher, the residual warm water amount is 6 at maximum.

(15-1-2-3) Circulating Water Pipe

The circulating water pipe 30 is a circuit for transferring heat obtained by the heat pump 2 to the water in the warm-water storage tank 35, and includes an outgoing pipe 31, the water pipe 32 w in the water heat exchanger 22, a return pipe 33, and a circulation pump 34. The outgoing pipe 31 connects a portion near the lower end of the warm-water storage tank 35 and the upstream-side end of the water pipe 32 w in the water heat exchanger 22. The return pipe 33 connects the downstream-side end of the water pipe 32 w in the water heat exchanger 22 and a portion near the upper end of the warm-water storage tank 35. The circulation pump 34 is provided midway in the outgoing pipe 31. The circulation pump 34 is an electric pump of which the output is adjustable, and circulates water between the warm-water storage tank 35 and the water heat exchanger 22. Specifically, in the circulating water pipe 30, when the circulation pump 34 is driven in response to an instruction from the controller 50, water at low temperature present in a lower portion of the water in the warm-water storage tank 35 flows out to the outgoing pipe 31, increases in temperature by passing through the water pipe 32 w in the water heat exchanger 22, and returns to the portion near the upper end of the warm-water storage tank 35 via the return pipe 33. Accordingly, the boundary between high-temperature water and water at a lower temperature in the warm-water storage tank 35 moves from the upper side toward the lower side, and hence the amount of the high-temperature water in the warm-water storage tank 35 increases.

(15-1-2-4) Water-Intake Warm-Water Supply Pipe and Combustion Heating Device

The water-intake warm-water supply pipe 70 is a circuit for using the high-temperature water stored in the warm-water storage tank 35 while receiving supply with water from external city water or the like, and includes a water intake pipe 71, a warm-water supply pipe 73, a bypass pipe 74, and the mixing valve 77.

The water intake pipe 71 receives supply with water from the external city water or the like, supplies normal-temperature water to a portion near the lower end of the warm-water storage tank 35. The water intake pipe 71 is provided with a water-intake temperature sensor 71T for detecting the temperature of the water supplied by the city water.

The warm-water supply pipe 73 guides high-temperature water which is included in the water stored in the warm-water storage tank 35 and which is present near the upper end, from the warm-water supply section 82 to an in-building pipe 99 a through a portion to be used by a user, for example, the faucet 99 in the building.

The combustion heating device 4 is disposed midway in the warm-water supply pipe 73. The combustion heating device 4 is disposed between the warm-water storage tank 35 and the mixing valve 77, and includes a combustion burner 41 that burns a fuel gas. The combustion burner 41 is a gas burner of which the heating capacity is adjustable, and heats water flowing through the warm-water supply pipe 73 while adjusting the heating quantity in response to an instruction of the controller 50.

Moreover, a before-mixing warm-water temperature sensor 4T for detecting the temperature of the passing water is provided between the combustion heating device 4 and the mixing valve 77 in the warm-water supply pipe 73.

The bypass pipe 74 is a pipe for mixing normal-temperature water flowing through the water intake pipe 71 with water (warm water) flowing through the warm-water supply pipe 73. The bypass pipe 74 extends from the water intake pipe 71 to the warm-water supply pipe 73 and is connected to the warm-water supply pipe 73 via the mixing valve 77.

The mixing valve 77 is an adjustment valve that receives an instruction from the controller 50 and adjusts the mixing ratio of the high-temperature water (warm water) flowing through the warm-water supply pipe 73 and the normal-temperature water flowing through the bypass pipe 74.

(15-1-3) Controller and Remote Controller

The controller 50 is installed in the warm-water storage unit 3, is connected to actuators, such as the compressor 21, the electric expansion valve 23, the fan 24F, the mixing valve 77, the combustion burner 41, and the circulation pump 34, and sends operation instructions to the actuators. Moreover, the controller 50 is connected to sensors, such as the heat-exchanger inlet water temperature sensor 31T, the heat-exchanger outlet water temperature sensor 32T, the tank-temperature-distribution detection sensors T1 to T6, the water-intake temperature sensor 71T, and the before-mixing warm-water temperature sensor 4T, and acquires detection results from the sensors. Furthermore, the remote controller 90 is connected to the controller 50. The remote controller 90 receives a setting input from the user and provides information to the user.

As illustrated in FIG. 6C, the remote controller 90 is provided with a warm-water temperature setting section 91 for setting the temperature of required warm water (water), and a display section 92 that displays the set warm-water temperature and the amount of residual warm water.

(15-1-4) Characteristics of Warm-Water Supply System

In the warm-water supply system 1 according to the present embodiment, since the water heat exchanger 22 heats water using one of the above-described refrigerants A to D, efficiency is high. When the water to be supplied is hard water, a scale may be disadvantageously generated. However, when the water to be supplied is soft water, it is advantageous to employ the warm-water supply system 1 according to the present embodiment.

(15-1-5) First Modification of First Embodiment

Employing a warm-water supply system 1 a illustrated in FIG. 6D instead of the warm-water supply system 1 according to the first embodiment can suppress the disadvantage of generation of a scale. In the warm-water supply system 1 a in FIG. 6D, a heat pump 2 a includes an auxiliary circulating water pipe 60 that is not included in the heat pump 2 of the first embodiment. The auxiliary circulating water pipe 60 is provided with an auxiliary circulation pump 64. The water in the auxiliary circulating water pipe 60 takes heat from the refrigerant in the water heat exchanger 22, and radiates heat to the water flowing through the main circulating water pipe 30 in the auxiliary water heat exchanger 62. The main water heat exchanger 22 is a heat exchanger that performs heat exchange between a refrigerant and water. The auxiliary water heat exchanger 62 is a heat exchanger that performs heat exchange between water and water.

In the warm-water supply system 1 a illustrated in FIG. 6D, the high-temperature gas refrigerant discharged from the compressor 21 of the heat pump 2 a heats, in the auxiliary water heat exchanger 62, the water flowing through the auxiliary circulating water pipe 60; and the heated water heats, in the auxiliary water heat exchanger 62, the water flowing through the main circulating water pipe 30. The flow path of water constituted by the auxiliary circulating water pipe 60 is a closed loop, and a scale is almost not generated in the closed loop.

(15-1-6) Second Modification of First Embodiment

Employing a warm-water supply system 1 b illustrated in FIG. 6E instead of the warm-water supply system 1 according to the first embodiment can suppress the disadvantage of generation of a scale. In the warm-water supply system 1 b in FIG. 6E, a warm-water storage unit 3 b includes a heat exchange section 38 that is not included in the warm-water storage unit 3 of the first embodiment. The heat exchange section 38 is a portion of a circulating water pipe 30 b and is disposed in the warm-water storage tank 35. In the warm-water supply system 1 according to the first embodiment, water flows out from a lower portion of the warm-water storage tank 35 to the circulating water pipe 30, and the heated water returns to a portion near the upper end of the warm-water storage tank 35. In contrast, in the warm-water supply system 1 b illustrated in FIG. 6E, the water in the warm-water storage tank 35 is boiled using the heated water flowing through the circulating water pipe 30 b constituting the closed loop. The water in the warm-water storage tank 35 takes heat from the warm water flowing through the heat exchange section 38, and hence the temperature thereof increases.

In the warm-water supply system 1 b illustrated in FIG. 6E, the flow path of water constituted by the circulating water pipe 30 b is a closed loop, and a scale is almost not generated in the closed loop.

Moreover, a heat pump 2 b of the warm-water supply system 1 b illustrated in FIG. 6E includes, in addition to the water heat exchanger 22 that functions as a use-side heat exchanger, a use-side water heat exchanger 22 a having a function similar to the water heat exchanger 22. The water heat exchanger 22 a is disposed on the upstream side of the flow of the refrigerant of the water heat exchanger 22, and heats the water flowing through a water circulation flow path 190. The water circulation flow path 190 is a closed loop flow path that connects a heat exchanger 192 disposed under a floor for floor heating and the water heat exchanger 22 a of the heat pump 2 b. The water circulation flow path 190 is provided with a pump 194. The water which has taken heat from and been heated by the high-temperature mixed refrigerant discharged from the compressor 21 in the water heat exchanger 22 a is sent to the heat exchanger 192 under the floor by driving of the pump 194. The water which has radiated heat in the heat exchanger 192 and performed floor heating passes through the water circulation flow path 190 and flows into the water heat exchanger 22 a again.

In this case, the heat pump 2 b contributes to warm-water supply by heating the water in the warm-water storage tank 35, and also serves as a heat source of floor heating.

(15-2) Second Embodiment (15-2-1) Major Configuration of Warm-Water Circulation Heating System

FIGS. 6F to 6H illustrate a configuration of a warm-water circulation heating system that is a warm-water generating apparatus according to a second embodiment. The warm-water circulation heating system performs heating by circulating warm water in a building and has a warm-water supply function. The warm-water circulation heating system includes a tank 240 that stores warm water, in-room radiators 261 a and 262 a, in-toilet radiators 269 b, 269 c, and 269 e, an indoor heating circulation pump 251, a vapor compression heat pump 210 for heating warm water, a warm-water heating circulation pump 225, a warm-water supply heat exchanger 241 a, a heated-water spray device 275, and a control unit 220.

The in-room radiators 261 a and 262 a are disposed in rooms 261 and 262 in the building, and radiate heat held by the warm water to the indoor airs in the rooms 261 and 262. The in-toilet radiators 269 b, 269 c, and 269 e are disposed in a toilet 269 in the building, and radiate heat held by the warm water in the toilet 269.

The indoor heating circulation pump 251 causes the warm water to flow from the tank 240 to the in-room radiators 261 a and 262 a and the in-toilet radiators 269 b, 269 c, and 269 e, and causes the warm water which has radiated heat in the in-room radiators 261 a and 262 a and the in-toilet radiators 269 b, 269 c, and 269 e to return to the tank 240 again. The warm water which has exited from the tank 240 flows through the in-room radiators 261 a and 262 a, then flows through the in-toilet radiators 269 b, 269 c, and 269 e, and returns to the tank 240.

The heat pump 210 includes a refrigerant circuit having a compressor 211, a radiator 212, an expansion valve 213, and an evaporator 214, takes heat from the outside air by the evaporator 214, and radiates heat from the radiator 212, thereby heating the warm water flowing from the tank 240. In the present embodiment, the refrigerant circuit is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and can use any one of the above-described refrigerants A to D.

The warm-water heating circulation pump 225 causes the warm water from the tank 240 to the radiator 212 of the heat pump 210, and causes the warm water to return from the radiator 212 of the heat pump 210 to the tank 240 again.

The warm-water supply heat exchanger 241 a is disposed in the tank 240, causes the water taken in from a water supply source and the warm water in the tank 240 to exchange heat with each other to heat water, and supplies the heated water to a warm-water supply pipe 272 in the building. The water which is heated in the warm-water supply heat exchanger 241 a and which is supplied to the warm-water supply pipe 272 is hereinafter referred to as heated water. Note that the water which is taken in from the water supply source and supplied to the warm-water supply pipe 272 is not mixed with the warm water in the tank 240. Reference sign 241 in FIG. 6F denotes a flow path of the water flowing from the water supply source to the warm-water supply pipe 272.

The heated-water spray device 275 is a device that sprays the heated water which is supplied from the warm-water supply heat exchanger 241 a to the warm-water supply pipe 272, onto the outer surface of the evaporator 214 of the heat pump 210.

Note that the warm water which is stored in the tank 240 and which circulates through the closed loop by the indoor heating circulation pump 251 and the warm-water heating circulation pump 225 uses normal water; however, may be a liquid and does not have to be water (H₂O). If there is a liquid which can decrease the powers of the indoor heating circulation pump 251 and the warm-water heating circulation pump 225 and which can decrease the sizes of the pipes 252, 231, and so forth, serving as a circulation route to be smaller than that for water (H₂O), the liquid is preferably used.

(15-2-2) Overview Operation of Warm-Water Circulation Heating System

In the warm-water circulation heating system, actuation of the warm-water heating circulation pump 225 causes the warm water flowing from the tank 240 to the radiator 212 of the heat pump 210 to be heated using heat radiated from the radiator 212 by actuation of the heat pump 210. Accordingly, the high-temperature warm water is returned from the heat pump 210 to the tank 240. In contrast, the warm water in the tank 240 is sent to the in-room radiators 261 a and 262 a in the rooms 261 and 262 and to the in-toilet radiators 269 b, 269 c, and 269 e in the toilet 269 by actuation of the indoor heating circulation pump 251. The heat of the warm water shifts to the indoor airs in the rooms 261 and 262 and to the vicinity of the in-toilet radiators 269 b, 269 c, and 269 e, thereby heating the rooms 261 and 262, and heating wash water in a toilet tank 269 a, a toilet seat 269 d, and the like, in the toilet 269. The warm water of which the temperature has decreased to about 10° C. to 20° C. is returned to the tank 240 again. The warm water whose temperature has decreased turns into high-temperature water again by actuation of the heat pump 210.

As described above, in this case, a first loop for circulation through the tank 240 and the heat pump 210 connected by a pipe 231, and a second loop for circulation through the tank 240, the in-room radiators 261 a and 262 a, and the in-toilet radiators 269 b, 269 c, and 269 e connected by a pipe 252 are formed. The warm water circulates through the loops. Thus, the heat collected from the outside by actuation of the heat pump 210 and the heat generated by actuation of the compressor 211 finally shift to the indoor airs in the rooms 261 and 262 and the respective sections of the toilet 269 via the warm water stored in the tank 240.

Moreover, the warm-water supply heat exchanger 241 a is disposed in the tank 240, the water taken in from the supply water source takes heat from the warm water in the tank 24 when passing through the warm-water supply heat exchanger 241 a and turns into the heated water, and the heated water flows to the warm-water supply pipe 272 in the building. The heated water flowing to the warm-water supply pipe 272 is to be used for a shower 273 and in a bathtub 274. Furthermore, part of the heated water which has flowed to the warm-water supply pipe 272 is sprayed onto the outer surface of the evaporator 214 of the heat pump 210 by the heated-water spray device 275. The spray is periodically performed under a predetermined condition that a frost is generated on the evaporator 214 of the heat pump 210.

(15-2-3) Detailed Configuration of Control Unit 220

As illustrated in FIGS. 6F and 6I, an overall controller 229 controls devices belonging to the heat pump 210 and devices belonging to the tank 240 based on signals input from the outside. The overall controller 229 is accommodated in a casing together with three-way valves 221 and 222 and the warm-water heating circulation pump 225 to form one control unit 220 (see FIG. 6F).

The three-way valves 221 and 222 are provided to adjust from which portion in the height direction of the tank 240 the warm water is to be drawn and sent to the in-room radiators 261 a and 262 a, and to which portion in the height direction of the tank 240 the low-temperature warm water returned from the in-toilet radiators 269 b, 269 c, and 269 e is returned. The three-way valves 221 and 222 are actuated in response to instructions from the overall controller 229.

The overall controller 229 controls, in addition to the three-way valves 221 and 222, a booster heater 242, a heat-pump control unit 219, the indoor heating circulation pump 251, the warm-water heating circulation pump 225, warm-water flow-rate adjustment valves 253 to 255, a defrost valve 277, and so forth. Moreover, the overall controller 229 receives signals of measurement results from a heating warm-water outgoing temperature sensor 252 a, a heating warm-water return temperature sensor 252 b, temperature sensors 240 a to 240 e of the tank 240, a water supply pipe temperature sensor 271 a, a warm-water supply pipe temperature sensor 272 a, and so forth; and receives information on the indoor temperature and the indoor set temperature from a remote controller/thermostat 291 disposed in the rooms 261 and 262, and so forth.

(15-2-4) Characteristics of Warm-Water Circulation Heating System

In the warm-water circulation heating system according to the second embodiment, since the radiator 212 of the heat pump 210 heats water using one of the above-described refrigerants A to D, efficiency is high. Moreover, the water to be heated by the radiator 212 of the heat pump 210 is stored in the tank 240 and circulates through the closed loop by the indoor heating circulation pump 251 and the warm-water heating circulation pump 225. In other words, the water which is heated by the radiator 212 of the heat pump 210 is not mixed with the water which is taken in from the water supply source and supplied to the warm-water supply pipe 272. Thus, an excessive scale is not generated by heating of water by the radiator 212 of the heat pump 210.

(15-2-5) First Modification of Second Embodiment

In the warm-water circulation heating system according to the second embodiment, the warm-water heat exchanger 241 a disposed in the tank 240 heats the water taken in from the water supply source to generate heated water for warm-water supply; however, as illustrated in FIG. 6J, a water heat exchanger 112 may generate heated water. In the warm-water circulation heating system illustrated in FIG. 6J, a water circulation flow path 110 and a pump 115 constituting a third loop are provided, warm water is taken out from an upper portion of the tank 240, the warm water passes through the water heat exchanger 112, and then the warm water from which heat is radiated is returned to a lower portion of the tank 240. In the water heat exchanger 112, the water taken in from the water supply source is heated by heat radiated from the warm water flowing from the tank 240, the water becomes heated water for warm-water supply, and the heated water flows to the warm-water supply pipe 272. Reference sign 118 in FIG. 6J denotes a flow path of water flowing from the water supply source to the warm-water supply pipe 272.

(15-2-6) Second Modification of Second Embodiment

In the warm-water circulation heating system according to the second embodiment, the warm water is fed from the lower portion of the tank 240 to the radiator 212 of the heat pump 210, and the warm water is returned from the radiator 212 of the heat pump 210 to the upper portion of the tank 240 again by the warm-water heating circulation pump 225. However, as illustrated in FIG. 6K, the radiator 212 may be omitted, a refrigerant circulation flow path 217 that guides a high-temperature high-pressure mixed refrigerant discharged from the compressor 211 to the inside of the tank 240 may be provided, and the water in the tank 240 may be heated by a heat exchanger 216 disposed in the tank 240. In the warm-water circulation heating system illustrated in FIG. 6K, the heat exchanger 216 in the tank 240 is disposed near a warm-water supply heat exchanger 241 a. The high-temperature refrigerant which has flowed through the refrigerant circulation flow path 217 radiates heat to the water in the tank 240 in the heat exchanger 216, is condensed and turns into a low-temperature high-pressure refrigerant in a liquid phase, and is returned to a unit of the heat pump 210. The liquid refrigerant returned to the unit of the heat pump 210 is decompressed at the expansion valve 213, flows into the evaporator 214, and takes heat from the outside air to be evaporated. Then, the mixed refrigerant is compressed in the compressor 211 again and turns into a high-temperature high-pressure mixed refrigerant. The water in the tank 240 heated by the heat exchanger 216 heats the water flowing through the warm-water supply heat exchanger 241 a that is adjacent to the heat exchanger 216. Moreover, the heat of the refrigerant is transferred to the warm-water supply heat exchanger 241 a also by radiation from the heat exchanger 216. The water taken in from the water supply source and flowing through the warm-water supply heat exchanger 241 a takes heat from the heat exchanger 216 via the water in the tank 240, takes heat from the heat exchanger 216 also by radiation, and hence the water becomes heated water.

In the warm-water circulation heating system illustrated in FIG. 6K, the water in the tank 240 is separated from the water flowing from the water supply source to the warm-water supply pipe 272 (water flowing through a flow path 241). Even when the heat exchanger 216 in the tank 240 that functions as the condenser of the mixed refrigerant rapidly heats the water, the amount of generation of a scale is less.

(15-3) Third Embodiment

FIG. 6L is a schematic configuration diagram of a warm-water supply system 310 serving as a warm-water generating apparatus according to a third embodiment. The warm-water supply system 310 is warm-water supply equipment used in a large-size facility, such as a hospital, a sport facility, or the like. As illustrated in FIG. 6L, the warm-water supply system 310 mainly includes a water receiving tank 320, a heat source unit 330, a warm-water storage tank 340, a warm-water use section 350, a control section 360, a water supply line 312, a warm-water exit line 314, and a warm-water circulation path 316. The water supply line 312 is a pipe that connects the water receiving tank 320 and the heat source unit 330. The warm-water exit line 314 is a pipe that connects the heat source unit 330 and the warm-water storage tank 340 to each other. The warm-water circulation path 316 is a pipe that connects the warm-water storage tank 340 and the warm-water use section 350 to each other. In FIG. 6L, arrows along the water supply line 312, the warm-water exit line 314, and the warm-water circulation path 316 represent directions in which water or warm water flows. Next, the water receiving tank 320, the heat source unit 330, the warm-water storage tank 340, the warm-water use section 350, and the control section 360 are described.

(15-3-1) Water Receiving Tank

The water receiving tank 320 is a tank for storing water to be used by the warm-water supply system 310. The water receiving tank 320 is connected to a water supply or the like. The water receiving tank 320 supplies water to the heat source unit 330 via the water supply line 312. The water-supply pressure of the water receiving tank 320 is 40 kPa to 500 kPa.

(15-3-2) Heat Source Unit

The heat source unit 330 is installed outside a room. The heat source unit 330 receives a supply with water from the water receiving tank 320 via the water supply line 312. The heat source unit 330 heats the water taken in from the water supply line 312. The heat source unit 330 sends warm water which is heated water to the warm-water storage tank 340 via the warm-water exit line 314.

FIG. 6M is a schematic configuration diagram of the heat source unit 330. FIG. 6N is a block diagram of the warm-water supply system 310. As illustrated in FIGS. 6M and 6N, the heat source unit 330 mainly includes a water flow path 331, a water supply pump 332, a second heat exchanger 333, a refrigerant circulation flow path 334, a compressor 335, an expansion valve 336, a first heat exchanger 337, and a warm-water exit temperature sensor 338. The water flow path 331 is connected to the water supply pump 332 and the second heat exchanger 333. The refrigerant circulation flow path 334 is connected to the compressor 335, the expansion valve 336, and the first heat exchanger 337. In FIG. 6M, arrows along the water flow path 331 and the refrigerant circulation flow path 334 represent directions in which the water or the refrigerant flows. Next, respective components of the heat source unit 330 are described.

(15-3-2-1) Water Flow Path

The water flow path 331 is a pipe through which the water taken in from the water supply line 312 flows. The water flow path 331 is constituted of a first water pipe 331 a, a second water pipe 331 b, and a third water pipe 331 c. The first water pipe 331 a is connected to the water supply line 312 and is also connected to the suction port of the water supply pump 332. The second water pipe 331 b is connected to the discharge port of the water supply pump 332 and is also connected to a water pipe 333 a of the second heat exchanger 333. The third water pipe 331 c is connected to the water pipe 333 a of the second heat exchanger 333 and is also connected to the warm-water exit line 314. The third water pipe 331 c is provided with the warm-water exit temperature sensor 338 for measuring the temperature of the water flowing through the third water pipe 331 c, at a position near the connection portion with respect to the warm-water exit line 314.

(15-3-2-2) Warm-water Supply Pump

The water supply pump 332 is a capacity variable pump, and hence can adjust the amount of water flowing through the water flow path 331. The water flowing through the water flow path 331 is supplied from the water supply line 312, passes through the water supply pump 332 and the second heat exchanger 333, and is supplied to the warm-water exit line 314.

(15-3-2-3) Second Heat Exchanger

The second heat exchanger 333 includes the water pipe 333 a through which the water flowing through the water flow path 331 passes, and a refrigerant pipe 333 b through which the refrigerant flowing through the refrigerant circulation flow path 334 passes. The second heat exchanger 333 is, for example, a tornado heat exchanger having a configuration in which the refrigerant pipe 333 b is wound around the outer periphery of the water pipe 333 a in a helical form and a groove is formed in the water pipe 333 a In the second heat exchanger 333, low-temperature water flowing through the water pipe 333 a and a high-temperature high-pressure refrigerant flowing through the refrigerant pipe 333 b exchange heat with each other. The low-temperature water flowing through the water pipe 333 a of the second heat exchanger 333 exchanges heat with the high-temperature refrigerant flowing through the refrigerant pipe 333 b of the second heat exchanger 333 and hence is heated. Accordingly, the water supplied from the water supply line 312 is heated in the second heat exchanger 333, and is supplied as warm water to the warm-water exit line 314.

(15-3-2-4) Refrigerant Circulation Flow Path

The refrigerant circulation flow path 334 is a pipe through which the refrigerant circulates, heat of the refrigerant being exchanged with heat of the water in the second heat exchanger 333. In the present embodiment, the refrigerant circulation flow path 334 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and can use any one of the above-described refrigerants A to D.

As illustrated in FIG. 6M, the refrigerant circulation flow path 334 couples the discharge port of the compressor 335 and the refrigerant pipe 333 b of the second heat exchanger 333 to each other, couples the refrigerant pipe 333 b of the second heat exchanger 333 and the expansion valve 336 to each other, couples the expansion valve 336 and the first heat exchanger 337 to each other, and couples the first heat exchanger 337 and the suction port of the compressor 335 to each other. The second heat exchanger 333 has a function as a condenser in a refrigeration cycle. The first heat exchanger 337 has a function as an evaporator in the refrigeration cycle.

(15-3-2-5) Compressor

The compressor 335 is a capacity variable inverter compressor. The compressor 335 sucks and compresses the low-pressure gas refrigerant flowing through the refrigerant circulation flow path 334. The high-temperature high-pressure gas refrigerant compressed in the compressor 335 is discharged from the compressor 335, and sent to the refrigerant pipe 333 b of the second heat exchanger 333. In the second heat exchanger 333, the high-temperature high-pressure gas refrigerant flowing through the refrigerant pipe 333 b of the second heat exchanger 333 exchanges heat with the low-temperature water flowing through the water pipe 333 a of the second heat exchanger 333. Thus, in the second heat exchanger 333, the high-temperature high-pressure gas refrigerant is condensed and turns into a high-pressure liquid refrigerant.

(15-3-2-6) Expansion Valve

The expansion valve 336 is an electric valve for adjusting the pressure and the flow rate of the refrigerant flowing through the refrigerant circulation flow path 334. The high-pressure liquid refrigerant which has exchanged heat in the refrigerant pipe 333 b of the second heat exchanger 333 is decompressed by passing through the expansion valve 336, and turns into a low-pressure refrigerant in a gas-liquid two-phase state.

(15-3-2-7) First Heat Exchanger

The first heat exchanger 337 is, for example, a plate fin-and-coil heat exchanger. A fan 337 a is provided near the first heat exchanger 337. The fan 337 a sends the outside air to the first heat exchanger 337, and discharges the outside air which has exchanged heat with the refrigerant in the first heat exchanger 337. In the first heat exchanger 337, the low-pressure refrigerant in a gas-liquid two-phase state decompressed at the expansion valve 336 is evaporated through heat exchange with the outside air supplied by the fan 337 a and turns into a low-pressure gas refrigerant. The low-pressure gas refrigerant which has passed through the first heat exchanger 337 is sent to the compressor 335.

(15-3-2-8) Warm-Water Exit Temperature Sensor

The warm-water exit temperature sensor 338 is a temperature sensor that is attached to the third water pipe 331 c, at a position near the connection portion between the third water pipe 331 c of the water flow path 331 and the warm-water exit line 314. The warm-water exit temperature sensor 338 measures the temperature of the water heated in the second heat exchanger 333 and flowing through the third water pipe 331 c. That is, the warm-water exit temperature sensor 338 measures the temperature of the warm water supplied by the heat source unit 330.

(15-3-3) Warm-Water Storage Tank

The warm-water storage tank 340 is an open warm-water storage tank for storing the warm water supplied from the heat source unit 330 via the warm-water exit line 314. The warm-water storage tank 340 is, for example, a tank made of stainless steel and a tank made of FRP. The warm water stored in the warm-water storage tank 340 is supplied to the warm-water use section 350 via the warm-water circulation path 316. As illustrated in FIG. 6L, the warm-water circulation path 316 is constituted of a first warm-water pipe 316 a and a second warm-water pipe 316 b. The warm-water storage tank 340 supplies the warm water stored therein to the first warm-water pipe 316 a, and sends the warm water to the warm-water use section 350 via the first warm-water pipe 316 a. The warm water which has not been used in the warm-water use section 350 is returned to the warm-water storage tank 340 via the second warm-water pipe 316 b. That is, part of the warm water stored in the warm-water storage tank 340 flows through the first warm-water pipe 316 a and the second warm-water pipe 316 b, and is returned to the warm-water storage tank 340 again.

Note that, as illustrated in FIG. 6L, a warm-water supply pump 351 is attached to the first warm-water pipe 316 a. The warm-water supply pump 351 is a pressure pump for sending the warm water stored in the warm-water storage tank 340 to the warm-water use section 350. The warm-water supply pump 351 is a capacity variable pump, and hence can adjust the amount of warm water to be sent to the warm-water use section 350.

As illustrated in FIG. 6N, the warm-water storage tank 340 mainly includes a heat retaining heater 341, a water-pressure sensor 342, a float switch 343, and a warm-water storage temperature sensor 344. Next, respective components of the warm-water storage tank 340 are described.

(15-3-3-1) Keep-Warm Heater

The heat retaining heater 341 is a heater attached to the inside of the warm-water storage tank 340 to retain the temperature of the warm water stored in the warm-water storage tank 340 at a temperature at which the warm water can be used as warm water in the warm-water use section 350 or higher. The warm-water storage tank 340 performs a heat retaining operation on the warm water stored therein using the heat retaining heater 341.

(15-3-3-2) Water-Pressure Sensor

The water-pressure sensor 342 is a sensor for measuring the residual amount of the warm water stored in the warm-water storage tank 340. The water-pressure sensor 342 is attached to a lower portion of the inside of the warm-water storage tank 340 and detects the water pressure due to the warm water in the warm-water storage tank 340, to calculate the residual amount and the water level of the warm water stored in the warm-water storage tank 340. The water-pressure sensor 342 can detect, for example, whether the residual amount of the warm water stored in the warm-water storage tank 340 is less than a target residual warm water amount which is previously set.

(15-3-3-3) Float Switch

The float switch 343 auxiliary detects the residual amount of the warm water stored in the warm-water storage tank 340 using a float that moves up and down in accordance with the water level of the warm water stored in the warm-water storage tank 340.

(15-3-3-4) Warm-Water Storage Temperature Sensor

The warm-water storage temperature sensor 344 is a temperature sensor that is installed in the warm-water storage tank 340, at a position near the connection portion between the first warm-water pipe 316 a of the warm-water circulation path 316 and the warm-water storage tank 340. The warm-water storage temperature sensor 344 measures the temperature of the warm water stored in the warm-water storage tank 340.

(15-3-4) Warm-Water Use Section

The warm-water use section 350 indicates places, such as a kitchen, a shower, a pool, and so forth, where the warm water stored in the warm water tank 340 is to be used. The warm water stored in the warm-water storage tank 340 is supplied to the warm-water use section 350 by the warm-water supply pump 351 via the first warm-water pipe 316 a of the warm-water circulation path 316. The warm-water use section 350 may not use all the warm water supplied via the first warm-water pipe 316 a. The warm water which has not been used in the warm-water use section 350 is returned to the warm-water storage tank 340 via the second warm-water pipe 316 b of the warm-water circulation path 316.

(15-3-5) Control Unit

As illustrated in FIG. 6N, the control section 360 is connected to a component of the warm-water supply system 310. Specifically, the control section 360 is connected to the water supply pump 332, the compressor 335, the expansion valve 336, the fan 337 a, the warm-water exit temperature sensor 338, the heat retaining heater 341, the water-pressure sensor 342, the float switch 343, the warm-water storage temperature sensor 344, and the warm-water supply pump 351. The control section 360 is installed in, for example, an electric component unit (not illustrated) in the heat source unit 330.

The control section 360 is a computer for controlling the components of the warm-water supply system 310. For example, the control section 360 controls the number of revolutions of the water supply pump 332, the operating frequency of the compressor 335, the opening degree of the expansion valve 336, the number of revolutions of the fan 337 a, the power consumption of the heat retaining heater 341, and the number of revolutions of the warm-water supply pump 351; and acquires measurement values of the warm-water exit temperature sensor 338, the water-pressure sensor 342, the float switch 343, and the warm-water storage temperature sensor 344.

Moreover, as illustrated in FIG. 6N, the control section 360 is connected to a remote controller 370. The remote controller 370 is a device for controlling the warm-water supply system 310.

(15-3-6) Characteristics of Warm-Water Supply System

In the warm-water supply system according to the third embodiment, since the second heat exchanger 333 of the heat source unit 330 heats water using one of the above-described refrigerants A to D, efficiency is high.

(17) Embodiment of the Technique of Seventeenth Group (17-1) First Embodiment

FIG. 7A is a schematic view showing a disposition of an air conditioning apparatus 1 according to a first embodiment. FIG. 7B is a schematic structural view of the air conditioning apparatus 1. In FIGS. 7A and 7B, the air conditioning apparatus 1 is a device that is used to air-condition houses or buildings.

Here, the air conditioning apparatus 1 is installed in a two-story house 100. The house 100 includes rooms 101 and 102 on the first floor and rooms 103 and 104 on the second floor. The house 100 includes abasement 105.

The air conditioning apparatus 1 is a so-called duct air conditioning system. The air conditioning apparatus 1 includes an indoor unit 2 that is a use-side unit, an outdoor unit 3 that is a heat-source-side unit, refrigerant connection pipes 306 and 307, and a first duct 209 that sends air that has been air-conditioned at the indoor unit 2 to the rooms 101 to 104. The first duct 209 branches into the rooms 101 to 104, and the branching portions are connected to ventilation ports 101 a to 104 a of the corresponding rooms 101 to 104. For convenience of explanation, the indoor unit 2, the outdoor unit 3, and the refrigerant connection pipes 306 and 307 are considered together as air conditioning equipment 80. The indoor unit 2 that is a use-side unit and the outdoor unit 3 that is a heat-source unit are different members.

In FIG. 7B, the indoor unit 2, the outdoor unit 3, and the refrigerant connection pipes 306 and 307 constitute a heat pump section 360 that heats an interior in a vapor compression refrigeration cycle. A gas furnace unit 205 that is a part of the indoor unit 2 constitutes a different heat source section 270 that heats the interior by using a heat source (here, heat by gas combustion) that differs from that of the heat pump section 360.

In this way, the indoor unit 2 includes the gas furnace unit 205 that constitutes the different heat source section 270 in addition to the members that constitute the heat pump section 360. The indoor unit 2 also includes an indoor fan 240 for introducing air in the rooms 101 to 104 into a casing 230 and suppling air that has been air-conditioned at the heat pump section 360 and the different heat source section 270 (the gas furnace unit 205) into the rooms 101 to 104. The indoor unit 2 is provided with a blow-out air temperature sensor 233 that detects a blow-out air temperature Trd that is the temperature of air in an air outlet 231 of the casing 230 and an indoor temperature sensor 234 that detects an indoor temperature Tr that is the temperature of air in an air inlet 232 of the casing 230. The indoor temperature sensor 234 may be provided in the rooms 101 to 104 instead of in the indoor unit 2. A second duct 210 is connected to the air inlet 232 of the casing 230. The indoor unit 2 that is a use-side unit includes the casing 230 and equipment that is accommodated therein. The indoor unit 2 is configured to guide indoor air F1 that is first air introduced from the interior to an indoor heat exchanger 242 that is a use-side heat exchanger.

(17-1-1) Heat Pump Section 360

In the heat pump section 360 of the air conditioning equipment 80, a refrigerant circuit 320 is formed by connecting the indoor unit 2 and the outdoor unit 3 via the refrigerant connection pipes 306 and 307. The refrigerant connection pipes 306 and 307 are refrigerant pipes that are constructed at a site when installing the air conditioning equipment 80.

The indoor unit 2 is installed in the basement 105 of the house 100. The location of installation of the indoor unit 2 is not limited to the basement 105, and may be other locations in the interior. The indoor unit 2 includes the indoor heat exchanger 242 that serves as a refrigerant heat dissipater that heats air by heat dissipation of a refrigerant in a refrigeration cycle, and an indoor expansion valve 241.

At the time of a cooling operation, the indoor expansion valve 241 decompresses a refrigerant that circulates in the refrigerant circuit 320 and causes the refrigerant to flow to the indoor heat exchanger 242. Here, the indoor expansion valve 241 is an electric expansion valve that is connected to a liquid side of the indoor heat exchanger 242.

The indoor heat exchanger 242 is disposed closest to a downwind side in a ventilation path extending from the air inlet 232, formed in the casing 230, to the air outlet 231, formed in the casing 230.

The outdoor unit 3 is installed outside the house 100. The outdoor unit 3 includes a compressor 321, an outdoor heat exchanger 323, an outdoor expansion valve 324, and a four-way valve 328. The compressor 321 is a hermetic compressor in which a compression element (not shown) and a compressor motor 322 that rotationally drives the compression element are accommodated in a casing.

The compressor motor 322 is configured so that electric power is supplied thereto via an inverter device (not shown), and an operating capacity can be varied by changing the frequency (that is, the number of rotations) of the inverter device.

The outdoor heat exchanger 323 is a heat exchanger that functions as a refrigerant evaporator that evaporates a refrigerant in a refrigeration cycle by using outdoor air. An outdoor fan 325 for sending outdoor air to the outdoor heat exchanger 323 is provided in the vicinity of the outdoor heat exchanger 323. The outdoor fan 325 is rotationally driven by an outdoor fan motor 326.

At the time of a heating operation, the outdoor expansion valve 324 decompresses a refrigerant that circulates in the refrigerant circuit 320 and causes the refrigerant to flow to the outdoor heat exchanger 323. Here, the outdoor expansion valve 324 is an electric expansion valve that is connected to a liquid side of the outdoor heat exchanger 323. The outdoor unit 3 is provided with an outdoor temperature sensor 327 that detects the temperature of outdoor air that exists at the outside of the house 100, where the outdoor unit 3 is disposed, that is, an outside air temperature Ta

In the present embodiment, the refrigerant circuit 320 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and any one of the refrigerants A to D above may be used.

The four-way valve 328 is a valve that switches the direction of flow of a refrigerant. At the time of the cooling operation, the four-way valve 328 connects a discharge side of the compressor 321 and a gas side of the outdoor heat exchanger 323, and connects a suction side of the compressor 321 and the gas refrigerant connection pipe 307 (a cooling operation state: refer to the solid line of the four-way valve 328 in FIG. 7B). As a result, the outdoor heat exchanger 323 functions as a condenser for a refrigerant, and the indoor heat exchanger 242 functions as an evaporator for a refrigerant.

At the time of the heating operation, the four-way valve 328 connects the discharge side of the compressor 321 and the gas refrigerant connection pipe 307, and connects the suction side of the compressor 321 and the gas side of the outdoor heat exchanger 323 (a heating operation state: refer to the broken line of the four-way valve 328 in FIG. 7B). As a result, the indoor heat exchanger 242 functions as a condenser for a refrigerant, and the outdoor heat exchanger 323 functions as an evaporator for a refrigerant.

(17-1-2) Outline of Important Structure of Air Conditioning Apparatus 1

When a heat pump heating operation is being performed, in the air conditioning apparatus 1, a refrigerant that contains at least 1,2-difluoroethylene circulates in the compressor 321, the indoor heat exchanger 242 that is a use-side heat exchanger, and the outdoor heat exchanger 323 that is a heat-source-side heat exchanger to repeat a refrigeration cycle. The indoor heat exchanger 242 causes heat to be exchanged between the indoor air F1 that is the first air, and the refrigerant. The indoor air F1 is supplied to the indoor heat exchanger 242 by the indoor fan 240. Indoor air F3 (the first air) that has been heated in the indoor heat exchanger 242 is sent to each of the rooms 101 to 104 from the indoor unit 2 via the first duct 209 to heat the rooms 101 to 104. The outdoor heat exchanger 323 causes heat to be exchanged between outdoor air that is second air, and the refrigerant. The casing 230 includes a use-side space SP2 that is connected to the first duct 209 and that accommodates the indoor heat exchanger 242, and is configured to allow the indoor air F3 that has exchanged heat with the refrigerant at the indoor heat exchanger 242 to be sent out to the first duct 209.

When a different heat source heating operation is being performed, a high-temperature combustion gas that has been sent to a furnace heat exchanger 255 exchanges heat with the indoor air F1 that is supplied by the indoor fan 240, is cooled, and becomes a low-temperature combustion gas in the furnace heat exchanger 255. The low-temperature combustion gas is discharged from the gas furnace unit 205 via a discharge pipe 257. On the other hand, the indoor air F2 that has been heated in the furnace heat exchanger 255 is sent to each of the rooms 101 to 104 from the indoor unit 2 via the first duct 209 to heat the rooms 101 to 104.

(17-1-3) Different Heat Source Section 270

The different heat source section 270 is constituted by the gas furnace unit 205 that is a part of the indoor unit 2 of the air conditioning equipment 80.

The gas furnace unit 205 is provided in the casing 230 that is installed in the basement 105 of the house 100. The gas furnace unit 205 is a gas-combustion heating device, and includes a fuel gas valve 251, a furnace fan 252, a combustion section 254, the furnace heat exchanger 255, an air supply pipe 256, and the discharge pipe 257.

The fuel gas valve 251 is, for example, an electromagnetic valve whose opening and closing are controllable, and is provided at a fuel gas supply pipe 258 that extends to the combustion section 254 from the outside of the casing 230. As the fuel gas, for example, natural gas or petroleum gas is used.

The furnace fan 252 is a fan that generates an airflow in which air is introduced into the combustion section 254 via the air supply pipe 256, then, the air is sent to the furnace heat exchanger 255, and the air is discharged from the discharge pipe 257. The furnace fan 252 is rotationally driven by a furnace fan motor 253.

The combustion section 254 is equipment that acquires a high-temperature combustion gas by igniting a mixed gas containing fuel gas and air by, for example, a gas burner (not shown).

The furnace heat exchanger 255 is a heat exchanger that heats air by heat dissipation of the combustion gas acquired at the combustion section 254, and functions as a different heat source heat dissipater that heats air by heat dissipation by using a heat source (here, heat by gas combustion) differing from that of the heat pump section 360.

The furnace heat exchanger 255 is disposed on an upwind side with respect to the indoor heat exchanger 242, serving as a refrigerant dissipater, in the ventilation path from the air inlet 232, formed in the casing 230, to the air outlet 231, formed in the casing 230.

(17-1-4) Indoor Fan 240

The indoor fan 240 is a fan for supplying air that is heated by the indoor heat exchanger 242, serving as a refrigerant heat dissipater, that constitutes the heat pump section 360 and by the furnace heat exchanger 255, serving as a different heat source dissipater, that constitutes the different heat source section 270 into the rooms 101 to 104.

In the ventilation path extending from the air inlet 232, formed in the casing 230, to the air outlet 231, formed in the casing 230, the indoor fan 240 is disposed on the upwind side with respect to both the indoor heat exchanger 242 and the furnace heat exchanger 255. The indoor fan 240 includes a blade 243 and a fan motor 244 that rotationally drives the blade 243.

(17-1-5) Controller 30

The indoor unit 2 is provided with an indoor-side control board 21 that controls the operation of each portion of the indoor unit 2. The outdoor unit 3 is provided with an outdoor-side control board 31 that controls the operation of each portion of the outdoor unit 3. The indoor-side control board 21 and the outdoor-side control board 31 each include, for example, a microcomputer, and each exchange, for example, control signals with a thermostat 40. Control signals are not exchanged between the indoor-side control board 21 and the outdoor-side control board 31. A control device including the indoor-side control board 21 and the outdoor-side control board 31 is called a controller 30.

(17-1-6) Detailed Structure of Controller 30

FIG. 7C is a block diagram showing an electrical connection state of the controller 30 and the thermostat 40 in the air conditioning apparatus 1 according to the first embodiment of the present invention. The thermostat 40 is mounted in an indoor space as with the indoor unit 2. The locations where the thermostat 40 and the indoor unit 2 are mounted may be different locations in the indoor space. The thermostat 40 is connected to a control system of the indoor unit 2 and a control system of the outdoor unit 3 by a communication line.

A transformer 20 applies a voltage of a commercial power source 90 after transformation to a usable low voltage to each of the indoor unit 2, the outdoor unit 3, and the thermostat 40 via power source lines 81 and 82.

(17-2) Second Embodiment (17-2-1) Overall Structure

As shown in FIG. 7D, an air conditioning apparatus 701 according to a second embodiment is installed on a roof 801 of a building 800, that is, on a rooftop. The air conditioning apparatus 701 is equipment that air-conditions the interior of the building 800. The building 800 includes a plurality of rooms 810. The rooms 810 of the building 800 are spaces to be air-conditioned by the air conditioning apparatus 701. FIG. 7D shows an example in which the air conditioning apparatus 701 includes one first duct 721 and one second duct 722. However, the air conditioning apparatus 701 may include a plurality of the first ducts 721 and a plurality of the second ducts 722. The first duct 721 shown in FIG. 7D is branched. The first duct 721 is provided for supply air, and the second duct 722 is provided for return air. Supply air that is supplied to the plurality of rooms 810 in the interior is first air. Return air that is introduced from the interior by the second duct 722 is also first air. In FIG. 7D, arrows Ar1 and Ar2 in the first duct 721 and the second duct 722 indicate the directions in which the air flows in the first duct 721 and the second duct 722. The air is sent to the rooms 810 from the air conditioning apparatus 701 via the first duct 721, and indoor air in the rooms 810, which is air in the spaces to be air-conditioned, is sent to the air conditioning apparatus 701 via the second duct 722. A plurality of blow-out ports 723 are each provided at a boundary between the first duct 721 and a corresponding one of the rooms 810. The supply air that is supplied by the first duct 721 is blown out to the rooms 810 from the blow-out ports 723. At least one suction port 724 is provided at a boundary between the second duct 722 and a corresponding room 810. The indoor air sucked in from the suction port 724 is return air that is returned to the air conditioning apparatus 701 by the second duct 722.

(17-2-2) External Appearance of Air Conditioning Apparatus 701

FIG. 7E shows an external appearance of the air conditioning apparatus 701 when seen from obliquely above the air conditioning apparatus 701, and FIG. 7F shows the external appearance of the air conditioning apparatus 701 when seen from obliquely below the air conditioning apparatus 701. For convenience, the air conditioning apparatus 701 is described below by using upward, downward, forward, rearward, left, and right directions indicated by arrows in the figures. The air conditioning apparatus 701 includes a casing 730 having a shape based on a parallelepiped. The casing 730 includes metal plates that cover an upper surface 730 a, a front surface 730 b, a right surface 730 c, a left surface 730 d, a rear surface 730 e, and a bottom surface 730 f. The casing 730 has a third opening 733 in the upper surface 730 a. The third opening 733 communicates with a heat-source-side space SP (see FIG. 7G). A heat-source-side fan 747 that blows out air in the heat-source-side space SP1 to the outside of the casing 730 via the third opening 733 is mounted in the third opening 733. As the heat-source-side fan 747, for example, a propeller fan is used. The casing 730 has slits 734 in the front surface 730 b, the left surface 730 d, and the rear surface 730 e. These slits 734 also communicate with the heat-source-side space SP1. Since, when the air is blown out toward the outer side of the casing 730 from the heat-source-side space SP1 by the heat-source-side fan 747, the pressure in the heat-source-side space SP1 becomes negative with respect to atmospheric pressure, outdoor air is sucked into the heat-source-side space SP1 from the outside of the casing 730 via the slits 734. The third opening 733 and the slits 734 do not communicate with a use-side space SP2 (see FIG. 7G). Therefore, in an ordinary state, other than the first duct 721 and the second duct 722, there are no portions that communicate with the outside of the casing 730 from the use-side space SP2.

A bottom plate 735 having a first opening 731 and a second opening 732 is mounted on the bottom surface 730 f of the casing 730. As shown in FIG. 7J, the first duct 721 is connected to the first opening 731 for supply air. As shown in FIG. 7J, the second duct 722 is connected to the second opening 732 for return air. Air that has returned to the use-side space SP2 of the casing 730 via the second duct 722 from the rooms 810, which are the spaces to be air conditioned, is sent to the rooms 810 via the first duct 721 from the use-side space SP2. For reinforcing the strength of the bottom plate 735, ribs 731 a and 732 a having a height of less than 3 cm are formed around the first opening 731 and the second opening 732 (see FIG. 7H). The ribs 731 a and 732 a are formed integrally with the bottom plate 735 by causing a metal plate, which is a material of the bottom plate 735, to stand by press-forming thereof when the first opening 731 and the second opening 732 are formed in the bottom plate 735 by, for example, press-forming thereof.

(17-2-3) Internal Structure of Air Conditioning Apparatus 701

(17-2-3-1) Heat-Source-Side Space SP1 and Use-Side Space SP2 in Casing 730

FIG. 7G shows a state in which the metal plate covering the front surface 730 b of the casing 730 and the metal plate covering the left surface 730 d of the casing 730 have been removed. FIG. 7H shows a state in which the metal plate covering the right surface 730 c of the casing 730 and the metal plate covering a part of the rear surface 730 e have been removed. In FIG. 7H, of the metal plate covering the rear surface 730 e, the removed part of the metal plate covering the rear surface 730 e is the metal plate covering the use-side space SP2. Therefore, the metal plate covering the rear surface 730 e shown in FIG. 7H only covers the heat-source-side space SP1. FIG. 7I shows a state in which the metal plate covering the right surface 730 c of the casing 730, the metal plate covering the left surface 730 d, and the metal plate covering a part of the upper surface 730 a have been removed, and a heat-source-side heat exchanger 743 and the heat-source-side fan 747 have been removed.

The heat-source space SP1 and the use-side space SP2 are separated by a partition plate 739. Outdoor air flows to the heat-source-side space SP1 and indoor air flows to the use-side space SP2. By separating the heat-source space SP1 and the use-side space SP2 by the partition plate 739, the flow of air between the heat-source space SP1 and the use-side space SP2 is blocked. Therefore, in an ordinary state, the indoor air and the outdoor air do not mix in the casing 730 and the interior and the exterior do not communicate with each other via the air conditioning apparatus 701.

(17-2-3-2) Structure in Heat-Source-Side Space SP1

The heat-source-side space SP1 accommodates, in addition to the heat-source-side fan 747, a compressor 741, a four-way valve 742, the heat-source-side heat exchanger 743, and an accumulator 746. The heat-source-side heat exchanger 743 includes a plurality of heat-transfer tubes (not shown) in which a refrigerant flows, and a plurality of heat-transfer fins (not shown) in which air flows between gaps thereof. The plurality of heat-transfer tubes are arranged in an up-down direction (hereunder may be referred to as “row direction”), and each heat-transfer tube extends in a direction substantially orthogonal to the up-down direction (in a substantially horizontal direction). The plurality of heat-transfer tubes are arranged in a plurality of columns in order from a side close to the casing 730. At an end portion of the heat-source-side heat exchanger 743, for example, the heat-transfer tubes are connected to each other by being bent into a U shape or by using a U-shaped tube so that the flow of a refrigerant from a certain column to another column and/or a certain row to another row is turned back. The plurality of heat-transfer fins that extend so as to be long in the up-down direction are arranged side by side in a direction in which the heat-transfer tubes extend with a predetermined interval between the plurality of heat-transfer fins. The plurality of heat-transfer fins and the plurality of heat-transfer tubes are assembled to each other so that each heat-transfer fin extends through the plurality of heat-transfer tubes. The plurality of heat-transfer fins are also disposed in a plurality of columns.

In top view, the heat-source-side heat exchanger 743 has a C shape, and is disposed opposite to the front surface 730 b, the left surface 730 d, and the rear surface 730 e of the casing 730. A portion that is not surrounded by the heat-source-side heat exchanger 743 is a portion that is opposite to the partition plate 739. Side end portions that are two ends of the C shape are disposed near the partition plate 739, and a portion between the two end portions of the heat-source-side heat exchanger 743 and the partition plate 739 is closed by a metal plate (not shown) that blocks air passage. The height of the heat-source-side heat exchanger 743 is substantially the same as the height from the bottom surface 730 f to the upper surface 730 a of the casing 730. Due to such a structure, a flow path of air that enters from the slits 734, passes through the heat-source-side heat exchanger 743, and exits from the third opening 733 is formed. When outdoor air sucked into the heat-source-side space SP1 via the slits 734 passes through the heat-source-side heat exchanger 743, the outdoor air exchanges heat with a refrigerant that flows in the heat-source-side heat exchanger 743. Air after the heat exchange by the heat-source-side heat exchanger 743 is discharged to the outside of the casing 730 from the third opening 733 by the heat-source-side fan 747.

(17-2-3-3) Structure in Use-Side Space SP2

An expansion valve 744, a use-side heat exchanger 745, and a use-side fan 748 are disposed in the use-side space SP2. As the use-side fan 748, for example, a centrifugal fan is used. As a centrifugal fan, for example, a sirocco fan exists. The expansion valve 744 may be disposed in the heat-source-side space SP1. As shown in FIG. 7H, the use-side fan 748 is disposed above the first opening 731 by a support base 751. As shown in FIG. 7N, in top view, a blow-out port 748 b of the use-side fan 748 is disposed at a location so as not to overlap the first opening 731. Since portions other than the blow-out port 748 b of the use-side fan 748 and the first opening 731 are surrounded by the support base 751 and the casing 730, substantially the entire air that is blown out from the blow-out port 748 b of the use-side fan 748 is supplied into the interior via the first duct 721 from the first opening 731.

The use-side heat exchanger 745 includes a plurality of heat-transfer tubes 745 a (see FIG. 7M) in which a refrigerant flows, and a plurality of heat-transfer fins (not shown) in which air flows between gaps thereof. The plurality of heat-transfer tubes 745 a are arranged in an up-down direction (row direction), and each heat-transfer tube 745 a extends in a direction substantially orthogonal to the up-down direction (in the second embodiment, in a left-right direction). Here, a refrigerant flows in the left-right direction in the plurality of heat-transfer tubes 745 a. The plurality of heat-transfer tubes 745 a are provided in a plurality of columns in a front-rear direction. At an end portion of the use-side heat exchanger 745, for example, the heat-transfer tubes 745 a are connected to each other by being bent into a U shape or by using a U-shaped tube so that the flow of a refrigerant from a certain column to another column and/or a certain row to another row is turned back. The plurality heat-transfer fins that extend so as to be long in the left-right direction are arranged in a direction in which the heat-transfer tubes 745 a extend with a predetermined interval between the plurality of heat-transfer fins. The plurality of heat-transfer fins and the plurality of heat-transfer tubes 745 a are assembled to each other so that each heat-transfer fin extends through the plurality of heat-transfer tubes 745 a. For example, a copper tube is used for each heat-transfer tube 745 a that constitutes the use-side heat exchanger 745 and aluminum may be used for each heat-transfer fin.

The use-side heat exchanger 745 has a shape that is short in the front-rear direction and long in the up-down direction and the left-right direction. A drain pan 752 has a shape like a shape formed by removing an upper surface of a parallelepiped that extends so as to be long in the left-right direction. In top view, the drain pan 752 has a front-rear-direction dimension that is longer than a front-rear length of the use-side heat exchanger 745. The use-side heat exchanger 745 is fitted in such a drain pan 752. The drain pan 752 receives dew condensation water that is produced at the use-side heat exchanger 745 and that falls dropwise downward. The drain pan 752 extends to the partition plate 739 from the right surface 730 c of the casing 730. A drainage port 752 a of the drain pan 752 extends through the right surface 730 c of the casing 730, and the dew condensation water received by the drain pan 752 passes through the drainage port 752 a and is caused to drain away to the outside of the casing 730.

The use-side heat exchanger 745 extends up to the vicinity of the partition plate 739 from the vicinity of the right surface 730 c of the casing 730. A portion between the right surface 730 c of the casing 730 and a right portion 745 c of the use-side heat exchanger 745 and a portion between the partition plate 739 and a left portion 745 d of the use-side heat exchanger 745 are closed by metal plates. The drain pan 752 is supported by a support frame 736 at a height h1 from the bottom plate 735 so as to be upwardly separated from the bottom plate 735. A support of the use-side heat exchanger 745 includes rod-shaped frame members combined around the upper, lower, left, and right sides of the use-side heat exchanger 745, and is helped by an auxiliary frame 753 that is directly or indirectly fixed to the casing 730 and the partition plate 739. A portion between the use-side heat exchanger 745 and the upper surface 730 a of the casing 730 is closed by the use-side heat exchanger 745 itself or the auxiliary frame 753. An opening portion between the use-side heat exchanger 745 and the bottom plate 735 is closed by the support base 751 and the drain pan 752.

In this way, the use-side heat exchanger 745 divides the use-side space SP2 into a space on an upstream side with respect to the use-side heat exchanger 745 and a space on a downstream side with respect to the use-side heat exchanger 745. All air that flows to the downstream side from the upstream side with respect to the use-side heat exchanger 745 passes through the use-side heat exchanger 745. The use-side fan 748 is disposed in the space on the downstream side with respect to the use-side heat exchanger 745 and causes an airflow that passes through the use-side heat exchanger 745 to be generated. The support base 751 that has been already described further divides the space on the downstream side with respect to the use-side heat exchanger 745 into a space on a suction side of the use-side fan 748 and a space on a blow-out side of the use-side fan 748.

(17-2-3-4) Refrigerant Circuit

FIG. 7K illustrates a refrigerant circuit 711 that is formed in the air conditioning apparatus 701. The refrigerant circuit 711 includes the use-side heat exchanger 745 and the heat-source-side heat exchanger 743. In the refrigerant circuit 711, a refrigerant circulates between the use-side heat exchanger 745 and the heat-source-side heat exchanger 743. In the refrigerant circuit 711, when, in a cooling operation or a heating operation, a vapor compression refrigeration cycle is performed, heat is exchanged at the use-side heat exchanger 745 and the heat-source-side heat exchanger 743. In FIG. 7K, an arrow Ar3 denotes supply air which is an airflow that is on the downstream side with respect to the use-side heat exchanger 745 and that is blown out from the use-side fan 748, and an arrow Ar4 denotes return air which is an airflow that is on the upstream side with respect to the use-side heat exchanger 745. An arrow Ar5 denotes an airflow that is on a downstream side with respect to the heat-source-side heat exchanger 743 and that is blown out from the third opening 733 by the heat-source-side fan 747, and an arrow Ar6 denotes an airflow that is on an upstream side with respect to the heat-source-side heat exchanger 743 and that is sucked from the slits 734 by the heat-source-side fan 747.

The refrigerant circuit 711 includes the compressor 741, the four-way valve 742, the heat-source-side heat exchanger 743, the expansion valve 744, the use-side heat exchanger 745, and the accumulator 746. The four-way valve 742 is switched to a connection state indicated by a solid line at the time of the cooling operation, and is switched to a connection state indicated by a broken line at the time of the heating operation.

At the time of the cooling operation, a gas refrigerant compressed by the compressor 741 passes through the four-way valve 742 and is sent to the heat-source-side heat exchanger 743. The refrigerant dissipates heat to outdoor air at the heat-source-side heat exchanger 743, passes along a refrigerant pipe 712, and is sent to the expansion valve 744. At the expansion valve 744, the refrigerant expands and is decompressed, passes along the refrigerant pipe 712, and is sent to the use-side heat exchanger 745. A refrigerant having a low temperature and a low pressure sent from the expansion valve 744 exchanges heat at the use-side heat exchanger 745, and takes away heat from indoor air. The air cooled by having its heat taken away at the use-side heat exchanger 745 passes through the first duct 721 and is supplied to the rooms 810. The gas refrigerant after the heat exchange at the use-side heat exchanger 745 or a gas-liquid two-phase refrigerant passes through a refrigerant pipe 713, the four-way valve 742, and the accumulator 746, and is sucked into the compressor 741.

At the time of the heating operation, a gas refrigerant compressed at the compressor 741 passes through the four-way valve 742 and the refrigerant pipe 713 and is sent to the use-side heat exchanger 745. The refrigerant exchanges heat with indoor air at the use-side heat exchanger 745 and applies heat to the indoor air. The air heated by the application of heat at the use-side heat exchanger 745 passes through the first duct 721 and is supplied to the rooms 810. The refrigerant after the heat exchange at the use-side heat exchanger 745 passes along the refrigerant pipe 712 and is sent to the expansion valve 744. A refrigerant having a low temperature and a low pressure that has expanded and that has been decompressed at the expansion valve 744 passes along the refrigerant pipe 712, is sent to the heat-source-side heat exchanger 743, exchanges heat at the heat-source-side heat exchanger 743, and acquires heat from outdoor air. The gas refrigerant after the heat exchange at the heat-source-side heat exchanger 743 or a gas-liquid two-phase refrigerant passes through the four-way valve 742 and the accumulator 746, and is sucked into the compressor 741.

(17-2-3-5) Control System

FIG. 7L illustrates, for example, a main controller 760 that controls the air conditioning apparatus 701 and main pieces of equipment that are controlled by the main controller 760. The main controller 760 controls the compressor 741, the four-way valve 742, the heat-source-side fan 747, and the use-side fan 748. The main controller 76) is configured to be capable of communicating with a remote controller 762. A user can send, for example, set values of indoor temperatures of the rooms 810 to the main controller 760 from the remote controller 762.

For controlling the air conditioning apparatus 701, a plurality of temperature sensors for measuring the temperature of a refrigerant at each portion of the refrigerant circuit 711 and/or a pressure sensor that measures the pressure of each portion and a temperature sensor for measuring the air temperature of each location are provided.

The main controller 760 performs at least on/off control of the compressor 741, on/off control of the heat-source-side fan 747, and on/off control of the use-side fan 748. When any or all of the compressor 741, the heat-source-side fan 747, and the use-side fan 748 include a motor of a type whose number of rotations is changeable, the main controller 760 may be configured to be capable of controlling the number of rotations of the motor or motors whose number of rotations is changeable among the motors of the compressor 741, the heat-source-side fan 747, and the use-side fan 748. In this case, the main controller 760 can control the circulation amount of the refrigerant that flows through the refrigerant circuit 711 by changing the number of rotations of the motor of the compressor 741. The main controller 760 can change the flow rate of outdoor air that flows between the heat-transfer fins of the heat-source-side heat exchanger 743 by changing the number of rotations of the motor of the heat-source-side fan 747. The main controller 760 can change the flow rate of indoor air that flows between the heat-transfer fins of the use-side heat exchanger 745 by changing the number of rotations of the motor of the use-side fan 748.

A refrigerant leakage sensor 761 is connected to the main controller 760. When the concentration of a refrigerant gas that has leaked into air becomes greater than or equal to a detected lower limit concentration, the refrigerant leakage sensor 761 sends a signal indicating the detection of the leakage of the gas refrigerant to the main controller 760.

The main controller 760 is realized by, for example, a computer. The computer that constitutes the main controller 760 includes a control calculation device and a storage device. For the control calculation device, a processor such as a CPU or a GPU may be used. The control calculation device reads a program that is stored in the storage device and performs a predetermined image processing operation and a computing processing operation in accordance with the program. Further, the control calculation device writes a calculated result to the storage device and reads information stored in the storage device in accordance with the program. However, the main controller 760 may be formed by using an integrated circuit (IC) that can perform control similar to the control that is performed by using a CPU and a memory. Here, IC includes, for example, LSI (large-scale integrated circuit), ASIC (application-specific integrated circuit), a gate array, and FPGA (field programmable gate array).

In the present embodiment, the refrigerant circuit 711 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and any one of the refrigerants A to D above may be used.

(17-3) Third Embodiment

FIG. 7O illustrates a structure of an air conditioning apparatus 601 according to a third embodiment. The air conditioning apparatus 601 is configured to perform indoor ventilation and humidity conditioning. A sensible heat exchanger 622 is provided in a central portion inside a casing 621 of the air conditioning apparatus 601. The sensible heat exchanger 622 does not exchange moisture between circulating air and circulating air. The sensible heat exchanger 622 has the function of exchanging sensible heat.

The air conditioning apparatus 601 includes a compressor 633, an outdoor heat exchanger 634 that is a heat-source-side heat exchanger, an air supply heat exchanger 625 that is a use-side heat exchanger, an air supply duct 651 that supplies supply air SA to a plurality of rooms in an interior, a return-air duct 652 that introduces indoor air RA from the interior, a suction duct 653 that introduces outdoor air OA from an exterior, and the casing 621. First air before heat exchange with a refrigerant at the air supply heat exchanger 625 is the outdoor air OA, and first air after the heat exchange with the refrigerant at the air supply heat exchanger 625 is the supply air SA. Outdoor air that is subjected to heat exchange at the outdoor heat exchanger 634 is second air. The outdoor air that is the second air and the outdoor air OA that is the first air differ from each other.

A refrigerant that contains at least 1,2-difluoroethylene circulates in the compressor 633, the air supply heat exchanger 625, and the outdoor heat exchanger 634, and a refrigeration cycle is repeated. More specifically, the refrigerant is compressed at the compressor 633, is condensed at the outdoor heat exchanger 634, is decompressed at a capillary tube 636, and is evaporated at the air supply heat exchanger 625. An evaporation valve may be used instead of the capillary tube 636.

A space including an air supply passage 641 and an outside air passage 643 in the casing 621 is a use-side space that is connected to the air supply duct 651 and that accommodates the air supply heat exchanger 625. The casing 621 is configured to be capable of allowing the supply air SA (the first air) after the heat exchange with the refrigerant at the air supply heat exchanger 625 to be sent out to the air supply duct 651. The air supply duct 651 is a first duct, and the suction duct 653 is a third duct.

Looking at it differently, the air conditioning apparatus 601 may be regarded as including a use-side unit 602 and a heat-source-side unit 603. The use-side unit 602 and the heat-source-side unit 603 are different units. The use-side unit 602 includes the casing 621, the sensible heat exchanger 622, the air supply heat exchanger 625, an exhaust fan 627, an air supply fan 628, and a humidifier 629. The heat-source-side unit 603 includes the compressor 633, the outdoor heat exchanger 634, and the capillary tube 636. The use-side unit 602 is configured to guide the outdoor air OA that is the first air introduced from the exterior to the air supply heat exchanger 625 that is a use-side heat exchanger with the casing 621 connected to the suction duct 653 that is the third duct.

The air supply passage 641 and a suction passage 644 are formed closer than the sensible heat exchanger 622 to an indoor side. An exhaust passage 642 and the outside air passage 643 are formed closer than the sensible heat exchanger 622 to an outdoor side. The air supply fan 628 and the humidifier 629 are provided in the air supply passage 641. The exhaust fan 627 is provided in the exhaust passage 642. The air supply heat exchanger 625 is provided in the outside air passage 643. The air supply heat exchanger 625 is connected to the heat-source-side unit 603. The compressor 633, the outdoor heat exchanger 634, and the capillary tube 636 that constitute a refrigerant circuit 610 along with the air supply heat exchanger 625 are provided in the heat-source-side unit 603. The compressor 633, the outdoor heat exchanger 634, and the capillary tube 636 are connected to a refrigerant pipe 645. An outdoor fan (not shown) is provided in parallel with the outdoor heat exchanger 634. In the air conditioning apparatus 601, the indoor air RA is sucked into the suction passage 644 by driving the exhaust fan 627, and the outdoor air OA is sucked into the outside air passage 643 by driving the air supply fan 628. At this time, the outdoor air OA sucked into the outside air passage 643 is cooled and dehumidified at the air supply heat exchanger 625 that functions as an evaporator, and reaches the sensible heat exchanger 622. In the sensible heat exchanger 622, the outdoor air OA exchanges sensible heat with the indoor air RA sucked into the suction passage 644. Due to the sensible heat exchange, the outdoor air OA is kept dehumidified and only its temperature becomes substantially equal to the temperature of the indoor air RA. The outdoor air OA is supplied into the interior as the supply air SA. On the other hand, the indoor air RA cooled at the sensible heat exchanger 622 is discharged to the exterior as exhaust EA.

The air conditioning apparatus 601 of the third embodiment cools the outdoor air OA at the air supply heat exchanger 625. The air cooled at the air supply heat exchanger 625 reaches the sensible heat exchanger 622. The air conditioning apparatus 601 causes the air cooled at the air supply heat exchanger 625 and the indoor air RA to exchange sensible heat at the sensible heat exchanger 622. The air conditioning apparatus 601 supplies the air that has exchanged sensible heat with the indoor air RA to be subsequently supplied as the supply air SA to the interior.

However, the structure of introducing the outdoor air is not limited thereto. For example, the air conditioning apparatus previously causes the outdoor air OA and the indoor air RA to exchange sensible heat at the sensible heat exchanger. Then, the air conditioning apparatus cools the air that has exchanged sensible heat with the indoor air RA at the use-side heat exchanger. The air conditioning apparatus supplies the air cooled at the use-side heat exchanger as the supply air SA into the interior.

The air conditioning apparatus may be configured to heat the outdoor air OA and supply the outdoor air OA into the interior so as to deal with seasons having low outdoor air temperatures. Such an air conditioning apparatus causes, for example, the outdoor air OA and the indoor air RA to exchange sensible heat at the sensible heat exchanger. The air conditioning apparatus then heats the air that has exchanged sensible heat with the indoor air RA at the use-side heat exchanger. The air conditioning apparatus supplies the air heated at the use-side heat exchanger as the supply air SA into the interior.

Since the air conditioning apparatus has a structure such as that described above, the outdoor air OA whose temperature has been previously adjusted at the sensible heat exchanger can be cooled or heated at the use-side heat exchanger afterwards, so that it is possible to increase the refrigeration cycle efficiency.

In the present embodiment, the refrigerant circuit 610 is filled with a refrigerant for performing a vapor compression refrigeration cycle. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and any one of the refrigerants A to D above may be used.

(17-4) Features

The air conditioning apparatus (1, 601, 701) of the first embodiment, the second embodiment, and the third embodiment above each include the compressor (321, 633, 741), the indoor heat exchanger 242, the air supply heat exchanger 625 or the use-side heat exchanger 745, the outdoor heat exchanger (323, 634) or the heat-source-side heat exchanger 743, any one of the refrigerants A to D, the first duct (209, 721) or the air supply duct 651, and the casing (230, 621, 730).

The indoor heat exchanger 242, the air supply heat exchanger 625, or the use-side heat exchanger 745 is a use-side heat exchanger that exchanges heat with the first air. The outdoor heat exchanger (323, 634) or the heat-source-side heat exchanger 743 is a heat-source-side heat exchanger that exchanges heat with the second air. The first duct (209, 721) or the air supply duct 651 is a first duct that supplies the first air into the plurality of rooms (101 to 104, 810). The refrigerants A to D contain at least 1,2-difluoroethylene, and circulate in the compressor, the use-side heat exchanger, and the heat-source-side heat exchanger to repeat the refrigeration cycle. The casings (230, 621, 730) each include the use-side space SP2 that is connected to the first duct (209, 721) or the air supply duct 651 and that accommodates the indoor heat exchanger 242, the air supply heat exchanger 625, or the use-side heat exchanger 745, and is configured to allow the first air after heat exchange with a refrigerant at the indoor heat exchanger 242, the air supply heat exchanger 625, or the use-side heat exchanger 745 to be sent out to the first duct (209, 721) or the air supply duct 651.

Since the air conditioning apparatus (1, 601, 701) having such a structure each supply the first air after heat exchange to the plurality of rooms via the first duct (209, 721) or the air supply duct 651, the structures of the refrigerant circuits (320, 711, 610) are simplified. Therefore, it is possible to reduce the amount of refrigerant with which the air conditioning apparatus (1, 601, 701) are filled.

(22) Embodiment of the Technique of Twenty-Second Group (22-1) Refrigeration Cycle Apparatus

Next, a refrigeration cycle apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.

The refrigeration cycle apparatus of the following embodiment of the present disclosure has a feature in which, at least during a predetermined operation, in at least one of a heat source-side heat exchanger and a usage-side heat exchanger, a flow of a refrigerant and a flow of a heating medium that exchanges heat with the refrigerant are counter flows. Hereinafter, to simplify description, a refrigeration cycle apparatus having such a feature is sometimes referred to as a refrigeration cycle apparatus including a counter-flow-type heat exchanger. Here, counter flow means that a flow direction of a refrigerant in a heat exchanger is opposite to a flow direction of an external heating medium (a heating medium that flows outside a refrigerant circuit). In other words, counter flow means that, in a heat exchanger, a refrigerant flows from the downstream side to the upstream side in a direction in which an external heating medium flows. In the following description, when a flow direction of a refrigerant in a heat exchanger is a forward direction with respect to a flow direction of an external heating medium; in other words, when a refrigerant flows from the upstream side to the downstream side in the direction in which an external heating medium flows, the flow of the refrigerant is referred to as a parallel flow.

The counter-flow-type heat exchanger will be described with reference to specific examples.

When an external heating medium is a liquid (for example, water), the heat exchanger is formed to be a double-pipe heat exchanger as illustrated in FIG. 8A(a), and a flow of a refrigerant and a flow of the external heating medium are enabled to be counter flows, for example, by causing the external heating medium to flow inside an inner pipe P1 of a double pipe from one side to the other side (in the illustration, from the upper side to the lower side) and by causing the refrigerant to flow inside an outer pipe P2 from the other side to the one side (in the illustration, from the lower side to the upper side). Alternatively, the heat exchanger is formed to be a heat exchanger in which a helical pipe P4 is coiled around the outer periphery of a cylindrical pipe P3 as illustrated in FIG. 8A(b), and a flow of a refrigerant and a flow of an external heating medium are enabled to be counter flows, for example, by causing the external heating medium to flow inside the cylindrical pipe P3 from one side to the other side (in the illustration, from the upper side to the lower side) and by causing the refrigerant to flow inside the helical pipe P4 from the other side to the one side (in the illustration, from the lower side to the upper side). Moreover, although illustration is omitted, counter flow may be realized by causing a flow direction of a refrigerant to be opposite to a flow direction of an external heating medium in another known heat exchanger such as a plate-type heat exchanger.

When an external heating medium is air, the heat exchanger can be formed to be, for example, a fin-and-tube heat exchanger as illustrated in FIG. 8B. The fin-and-tube heat exchanger includes, for example, as in FIG. 8B, a plurality of fins F that are arranged in parallel at a predetermined interval and U-shaped heat transfer tubes P5 meandering in plan view. In the fin-and-tube heat exchanger, linear portions parallel to each other that are included in the respective heat transfer tubes P5 and that are a plurality of lines (in FIG. 8B, two lines) are provided so as to penetrate the plurality of fins F. In both ends of each heat transfer tube P5, one end is to be an inlet for a refrigerant and the other end is to be an outlet for the refrigerant. As indicated by arrow X in the figure, a flow of the refrigerant in the heat exchanger and a flow of the external heating medium are enabled to be counter flows by causing the refrigerant to flow from the downstream side to the upstream side in the flow direction Y of the air.

The refrigerant that is sealed in the refrigerant circuit of the refrigeration cycle apparatus according to the present disclosure is a mixed refrigerant containing 1,2-difluoroethylene, and may be any one of the above-described refrigerants A to D can be used. During evaporation and condensation of each of the above-described refrigerants A to D, the temperature of the heating medium increases or decreases.

Such a refrigeration cycle involving temperature change (temperature glide) during evaporation and condensation is called the Lorentz cycle. In the Lorentz cycle, a temperature difference between the temperature of the refrigerant during evaporation and the temperature of the refrigerant during condensation is decreased by causing an evaporator and a condenser that function as heat exchangers performing heat exchange to be counter-flow types. However, it is possible to exchange heat efficiently because the temperature difference that is large enough to effectively transfer heat between the refrigerant and the external heating medium is maintained. In addition, another advantage of the refrigeration cycle apparatus including the counter-flow-type heat exchanger is that a pressure difference is also minimized. Therefore, in the refrigeration cycle apparatus including the counter-flow-type heat exchanger, improvement in energy efficiency and performance can be obtained compared with an existing system.

(22-1-1) First Embodiment

FIG. 8C is a schematic structural diagram of a refrigeration cycle apparatus 10 according to an embodiment.

Here, a case where a refrigerant and air as an external heating medium exchange heat with each other in a usage-side heat exchanger 15, which will be described below, of the refrigeration cycle apparatus 10 will be described as an example. However, the usage-side heat exchanger 15 may be a heat exchanger that performs heat exchange with a liquid (for example, water) as an external heating medium. Here, a case where a refrigerant and a liquid as an external heating medium exchange heat with each other in a heat source-side heat exchanger 13, which will be described below, of the refrigeration cycle apparatus 10 will be described as an example. However, the usage-side heat exchanger 15 may be a heat exchanger that performs heat exchange with air as an external heating medium. In other words, a combination of the external heating medium that exchanges heat with the refrigerant in the heat source-side heat exchanger 13 and the external heating medium that exchanges heat with the refrigerant in the usage-side heat exchanger 15 may be any one of the combinations: (liquid, air), (air, liquid), (liquid, liquid), and (air, air). The same applies to other embodiments.

Here, the refrigeration cycle apparatus 10 is an air conditioning apparatus. However, the refrigeration cycle apparatus 10 is not limited to an air conditioning apparatus, and may be, for example, a refrigerator, a freezer, a water cooler, an ice-making machine, a refrigerating showcase, a freezing showcase, a freezing and refrigerating unit, a refrigerating machine for a freezing and refrigerating warehouse or the like, a chiller (chilling unit), a turbo refrigerating machine, or a screw refrigerating machine.

Here, in the refrigeration cycle apparatus 10, the heat source-side heat exchanger 13 is used as a condenser for the refrigerant, the usage-side heat exchanger 15 is used as an evaporator for the refrigerant, and the external heating medium (in the present embodiment, air) is cooled in the usage-side heat exchanger 15. However, the refrigeration cycle apparatus 10 is not limited to this configuration. In the refrigeration cycle apparatus 10, the heat source-side heat exchanger 13 may be used as an evaporator for the refrigerant, the usage-side heat exchanger 15 may be used as a condenser for the refrigerant, and the external heating medium (in the present embodiment, air) may be heated in the usage-side heat exchanger 15. However, in this case, a flow direction of the refrigerant is opposite to that of FIG. 8C. In this case, counter flow is realized by causing a direction in which the external heating medium flows in each of the heat exchangers 13 and 15 to be also opposite to a corresponding direction in FIG. 8C. When the heat source-side heat exchanger 13 is used as an evaporator for the refrigerant and the usage-side heat exchanger 15 is used as a condenser for the refrigerant, although the use of the refrigeration cycle apparatus 10 is not limited, the refrigeration cycle apparatus 10 may be a hot water supply apparatus, a floor heating apparatus, or the like other than an air conditioning apparatus (heating apparatus).

The refrigeration cycle apparatus 10 includes a refrigerant circuit 11 in which a mixed refrigerant containing 1,2-difluoroethylene is sealed and through which the refrigerant is circulated. Any one of the above-described refrigerants A to D can be used for the mixed refrigerant containing 1,2-difluoroethylene.

The refrigerant circuit 11 includes mainly a compressor 12, the heat source-side heat exchanger 13, an expansion mechanism 14, and the usage-side heat exchanger 15 and is configured by connecting the pieces of equipment 12 to 15 one after another. In the refrigerant circuit 11, the refrigerant circulates in the direction indicated by solid-line arrows of FIG. 8C.

The compressor 12 is a piece of equipment that compresses a low-pressure gas refrigerant and discharges a gas refrigerant at a high-temperature and a high-pressure in the refrigeration cycle. The high-pressure gas refrigerant that has been discharged from the compressor 12 is supplied to the heat source-side heat exchanger 13.

The heat source-side heat exchanger 13 functions as a condenser that condenses the high-temperature and high-pressure gas refrigerant that is compressed in the compressor 12. The heat source-side heat exchanger 13 is disposed, for example, in a machine chamber. In the present embodiment, a liquid (here, cooling water) is supplied to the heat source-side heat exchanger 13 as an external heating medium. The heat source-side heat exchanger 13 is, but is not limited to, a double-pipe heat exchanger, for example. In the heat source-side heat exchanger 13, the high-temperature and high-pressure gas refrigerant condenses to become a high-pressure liquid refrigerant by heat exchange between the refrigerant and the external heating medium. The high-pressure liquid refrigerant that has passed through the heat source-side heat exchanger 13 is sent to the expansion mechanism 14.

The expansion mechanism 14 is a piece of equipment to decompress the high-pressure liquid refrigerant that has dissipated heat in the heat source-side heat exchanger 13 to a low pressure in the refrigeration cycle. For example, an electronic expansion valve is used as the expansion mechanism 14.

However, as illustrated in FIG. 8D, a thermosensitive expansion valve may be used as the expansion mechanism 14. When a thermosensitive expansion valve is used as the expansion mechanism 14, the thermosensitive expansion valve detects the temperature of the refrigerant after the refrigerant passes through the usage-side heat exchanger 15 by a thermosensitive cylinder directly connected to the expansion valve and controls the opening degree of the expansion valve based on the detected temperature of the refrigerant. Therefore, for example, when the usage-side heat exchanger 15, the expansion valve, and the thermosensitive cylinder are provided in the usage-side unit, control of the expansion valve is completed only within the usage-side unit. As a result, low cost and construction savings can be achieved because communications relevant to the control of the expansion valve are not needed between the heat source-side unit in which the heat source-side heat exchanger 13 is provided and the usage-side unit. When a thermosensitive expansion valve is used for the expansion mechanism 14, it is preferable to dispose an electromagnetic valve 17 on the heat source-side heat exchanger 13 side of the expansion mechanism 14.

Alternatively, the expansion mechanism 14 may be a capillary tube (not shown).

A low-pressure liquid refrigerant or a gas-liquid two-phase refrigerant that has passed through the expansion mechanism 14 is supplied to the usage-side heat exchanger 15.

The usage-side heat exchanger 15 functions as an evaporator that evaporates the low-pressure liquid refrigerant. The usage-side heat exchanger 15 is disposed in a target space that is to be air-conditioned. In the present embodiment, the usage-side heat exchanger 15 is supplied with air as an external heating medium by a fan 16. The usage-side heat exchanger 15 is, but is not limited to, a fin-and-tube heat exchanger, for example. In the usage-side heat exchanger 15, by heat exchange between the refrigerant and the air, the low-pressure liquid refrigerant evaporates to become a low-pressure gas refrigerant whereas the air as an external heating medium is cooled. The low-pressure gas refrigerant that has passed through the usage-side heat exchanger 13 is supplied to the compressor 12 and circulates through the refrigerant circuit 11 again.

In the above-described refrigeration cycle apparatus 10, both heat exchangers, which are the heat source-side heat exchanger 13 and the usage-side heat exchanger 15, are counter-flow-type heat exchangers during the operation.

<Features of Refrigeration Cycle Apparatus>

The refrigeration cycle apparatus 10 includes the refrigerant circuit 11 including the compressor 12, the heat source-side heat exchanger 13, the expansion mechanism 14, and the usage-side heat exchanger 15. In the refrigerant circuit 11, the refrigerant containing at least 1,2-difluoroethylene (HFO-1132 (E)) is sealed. At least during a predetermined operation, in at least one of the heat source-side heat exchanger 13 and the usage-side heat exchanger 15, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows.

The refrigeration cycle apparatus realizes highly efficient operation effectively utilizing the heat exchangers 13 and 15 by using the refrigerant that contains 1,2-difluoroethylene (HFO-1132 (E)) and that has a low global warming potential.

When each of the heat exchangers 13 and 15 functions as a condenser for the refrigerant, the temperature of the refrigerant that passes therethrough tends to be lower on the exit side than the temperature thereof on the entrance side. However, when each of the heat exchangers 13 and 15 that functions as a condenser is formed to be a counter-flow-type heat exchanger, a temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in each of the heat exchangers 13 and 15.

When each of the heat exchangers 13 and 15 functions as an evaporator for the refrigerant, the temperature of the refrigerant that passes therethrough tends to be higher on the exit side than a temperature thereof on the entrance side. However, when each of the heat exchangers 13 and 15 that functions as an evaporator is formed to be a counter-flow-type heat exchanger, the temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in each of the heat exchangers 13 and 15.

<Modifications>

As illustrated in FIG. 8E, in the refrigeration cycle apparatus 10, the refrigerant circuit 11 may include a plurality of (in the illustrated example, two) expansion mechanisms 14 parallel to each other and a plurality of (in the illustrated example, two) usage-side heat exchangers 15 parallel to each other. Although illustration is omitted, the refrigerant circuit 11 may include a plurality of heat source-side heat exchangers 13 that are arranged in parallel or may include a plurality of compressors 12.

As illustrated in FIG. 8F, in the refrigeration cycle apparatus 10, the refrigerant circuit 11 may further include a flow path switching mechanism 18. The flow path switching mechanism 18 is a mechanism that switches between the heat source-side heat exchanger 13 and the usage-side heat exchanger 15 as a destination to which the gas refrigerant that is discharged from the compressor 12 flows. For example, the flow path switching mechanism 18 is a four-way switching valve but is not limited to such a valve, and the flow path switching mechanism 18 may be realized by using a plurality of valves. The flow path switching mechanism 18 can switch between a cooling operation in which the heat source-side heat exchanger 13 functions as a condenser and the usage-side heat exchanger 15 functions as an evaporator and a heating operation in which the heat source-side heat exchanger 13 functions as an evaporator and the usage-side heat exchanger 15 functions as a condenser.

In an example illustrated in FIG. 8F, during the cooling operation, the heat source-side heat exchanger 13 functioning as a condenser and the usage-side heat exchanger 15 functioning as an evaporator both become counter-flow-type heat exchangers (refer to solid arrows indicating the refrigerant flow). In contrast, the heat source-side heat exchanger 13 functioning as an evaporator and the usage-side heat exchanger 15 functioning as a condenser both become parallel-flow-type heat exchangers (the flow direction of the refrigerant is the forward direction with respect to the flow direction of the external heating medium) during the heating operation (refer to dashed arrows indicating the refrigerant flow).

However, the configuration is not limited to such a configuration, and the flow direction of the external heating medium that flows in the heat source-side heat exchanger 13 may be designed so that the heat source-side heat exchanger 13 functioning as a condenser becomes a parallel-flow-type heat exchanger during the cooling operation and the heat source-side heat exchanger 13 functioning as an evaporator becomes a counter-flow-type heat exchanger during the heating operation. In addition, the flow direction of the external heating medium that flows in the usage-side heat exchanger 15 may be designed so that the usage-side heat exchanger 15 functioning as an evaporator becomes a parallel-flow-type heat exchanger during the cooling operation and the usage-side heat exchanger 15 functioning as a condenser becomes a counter-flow-type heat exchanger during the heating operation.

The flow direction of the external heating medium is preferably designed so that, when each of the heat exchangers 13 and 15 functions as a condenser, the flow direction of the refrigerant is opposite to the flow direction of the external heating medium. In other words, when each of the heat exchangers 13 and 15 functions as a condenser, the heat exchangers 13 and 15 are preferably counter-flow-type heat exchangers.

(22-1-2) Second Embodiment

Hereinafter, an air conditioning apparatus 100 as a refrigeration cycle apparatus according to a second embodiment will be described with reference to FIG. 8G, which is a schematic structural diagram of a refrigerant circuit, and FIG. 8H, which is a schematic control block structural diagram.

The air conditioning apparatus 100 is an apparatus that conditions the air in a target space by performing a vapor-compression refrigeration cycle.

The air conditioning apparatus 100 includes mainly a heat source-side unit 120, a usage-side unit 130, a liquid-side connection pipe 106 and a gas-side connection pipe 105 that both connect the heat source-side unit 120 to the usage-side unit 130, a remote controller, which is not illustrated, as an input device and an output device, and a controller 107 that controls the operations of the air conditioning apparatus 100.

A refrigerant for performing a vapor-compression refrigeration cycle is sealed in the refrigerant circuit 110. The air conditioning apparatus 100 performs a refrigeration cycle in which the refrigerant sealed in the refrigerant circuit 110 is compressed, cooled or condensed, decompressed, and, after being heated or evaporated, compressed again. The refrigerant is a mixed refrigerant containing 1,2-difluoroethylene, and may be any one of the above-described refrigerants A to D can be used. In addition, the refrigerant circuit 110 is filled with refrigerating machine oil with the mixed refrigerant.

(22-1-2-1) Heat Source-Side Unit

The heat source-side unit 120 is connected to the usage-side unit 130 through the liquid-side connection pipe 106 and the gas-side connection pipe 105 and constitutes a portion of the refrigerant circuit 110. The heat source-side unit 120 includes mainly a compressor 121, a flow path switching mechanism 122, a heat source-side heat exchanger 123, a heat source-side expansion mechanism 124, a low-pressure receiver 141, a heat source-side fan 125, a liquid-side shutoff valve 129, a gas-side shutoff valve 128, and a heat source-side bridge circuit 153.

The compressor 121 is a piece of equipment that compresses the refrigerant at a low pressure in the refrigeration cycle to a high pressure in the refrigeration cycle. Here, a compressor that has a hermetically sealed structure and a positive-displacement compression element (not shown) such as a rotary type or a scroll type is rotatably driven by a compressor motor is used as the compressor 121. The compressor motor is for changing capacity, and it is possible to control operation frequency by using an inverter. The compressor 121 includes an accompanying accumulator, which is not illustrated, on the suction side.

The flow path switching mechanism 122 is, for example, a four-way switching valve. By switching connection states, the flow path switching mechanism 122 can switch between a cooling-operation connection state in which a discharge side of the compressor 121 is connected to the heat source-side heat exchanger 123 and a suction side of the compressor 121 is connected to the gas-side shutoff valve 128 and a heating-operation connection state in which the discharge side of the compressor 121 is connected to the gas-side shutoff valve 128 and the suction side of the compressor 121 is connected to the heat source-side heat exchanger 123.

The heat source-side heat exchanger 123 is a heat exchanger that functions as a condenser for the refrigerant at a high pressure in the refrigeration cycle during the cooling operation and that functions as an evaporator for the refrigerant at a low pressure in the refrigeration cycle during the heating operation.

After the heat source-side fan 125 causes the heat source-side unit 120 to suck air that is to be a heat source thereinto and the air exchanges heat with the refrigerant in the heat source-side heat exchanger 123, the heat source-side fan 125 generates an air flow to discharge the air to outside. The heat source-side fan 125 is rotatably driven by an outdoor fan motor.

The heat source-side expansion mechanism 124 is provided between a liquid-side end portion of the heat source-side heat exchanger 123 and the liquid-side shutoff valve 129. The heat source-side expansion mechanism 124 may be a capillary tube or a mechanical expansion valve that is used with a thermosensitive cylinder but is preferably an electrically powered expansion valve whose valve opening degree can be regulated by being controlled.

The low-pressure receiver 141 is provided between the suction side of the compressor 121 and one of the connection ports of the flow path switching mechanism 122 and is a refrigerant container capable of storing surplus refrigerant as a liquid refrigerant in the refrigerant circuit 110. In addition, the compressor 121 includes the accompanying accumulator, which is not illustrated, and the low-pressure receiver 141 is connected to the upstream side of the accompanying accumulator.

The liquid-side shutoff valve 129 is a manual valve disposed in a connection portion in the heat source-side unit 120 with the liquid-side connection pipe 106.

The gas-side shutoff valve 128 is a manual valve disposed in a connection portion in the heat source-side unit 120 with the gas-side connection pipe 105.

The heat source-side bridge circuit 153 includes four connection points and check valves provided between the respective connection points. A refrigerant pipe extending from an inflow side of the heat source-side heat exchanger 123, a refrigerant pipe extending from an outflow side of the heat source-side heat exchanger 123, a refrigerant pipe extending from the liquid-side shutoff valve 129, and a refrigerant pipe extending from one of the connection ports of the flow path switching mechanism 122 are connected to the respective connection points of the heat source-side bridge circuit 153. A corresponding check valve blocks the refrigerant flow from one of the connection ports of the flow path switching mechanism 122 to the outflow side of the heat source-side heat exchanger 123, a corresponding check valve blocks the refrigerant flow from the liquid-side shutoff valve 129 to the outflow side of the heat source-side heat exchanger 123, a corresponding check valve blocks the refrigerant flow from the inflow side of the heat source-side heat exchanger 123 to one of the connection ports of the flow path switching mechanism 122, and a corresponding check valve blocks the refrigerant flow from the inflow side of the heat source-side heat exchanger 123 to the liquid-side shutoff valve 129. The heat source-side expansion mechanism 124 is provided in the middle of the refrigerant pipe extending from the liquid-side shutoff valve 129 to one of the connection points of the heat source-side bridge circuit 153.

In FIG. 8G, the air flow formed by the heat source-side fan 125 is indicated by dotted arrows. Here, in both cases in which the heat source-side heat exchanger 123 of the heat source-side unit 120 including the heat source-side bridge circuit 153 functions as an evaporator for the refrigerant and as a condenser for the refrigerant, the heat source-side heat exchanger 123 is configured so that a point (on the downstream side of the air flow) into which the refrigerant flows at the heat source-side heat exchanger 123 is the same, a point (on the upstream side of the air flow) at which the refrigerant flows out from the heat source-side heat exchanger 123 is the same, and the direction in which the refrigerant flows in the heat source-side heat exchanger 123 is the same. Therefore, in both cases in which the heat source-side heat exchanger 123 functions as an evaporator for the refrigerant and in which the heat source-side heat exchanger 123 functions as a condenser for the refrigerant, the flow direction of the refrigerant that flows in the heat source-side heat exchanger 123 is to be opposite to the direction of the air flow formed by the heat source-side fan 125 (counter flow at all the time).

The heat source-side unit 120 includes a heat source-side unit control section 127 that controls the operation of each component constituting the heat source-side unit 120. The heat source-side unit control section 127 includes a microcomputer including a CPU, memory, and the like. The heat source-side unit control section 127 is connected to a usage-side unit control section 134 of each usage-side unit 130 through a communication line and sends and receives control signals or the like.

A discharge pressure sensor 161, a discharge temperature sensor 162, a suction pressure sensor 163, a suction temperature sensor 164, a heat source-side heat-exchanger temperature sensor 165, a heat source air temperature sensor 166, and the like are provided in the heat source-side unit 120. Each sensor is electrically coupled to the heat source-side unit control section 127 and sends a detection signal to the heat source-side unit control section 127. The discharge pressure sensor 161 detects the pressure of the refrigerant that flows through a discharge pipe that connects the discharge side of the compressor 121 to one of the connection ports of the flow path switching mechanism 122. The discharge temperature sensor 162 detects the temperature of the refrigerant that flows through the discharge pipe. The suction pressure sensor 163 detects the pressure of the refrigerant that flows through a suction pipe that connects the low-pressure receiver 141 to the suction side of the compressor 121. The suction temperature sensor 164 detects the temperature of the refrigerant that flows through the suction pipe. The heat source-side heat-exchanger temperature sensor 165 detects the temperature of the refrigerant that flows through an exit on a liquid side of the heat source-side heat exchanger 123 that is opposite to a side to which the flow path switching mechanism 122 is connected. The heat source air temperature sensor 166 detects the air temperature of heat source air before the heat source air passes through the heat source-side heat exchanger 123.

(22-1-2-2) Usage-Side Unit

The usage-side unit 130 is installed on a wall surface, a ceiling, or the like of the target space that is to be air-conditioned. The usage-side unit 130 is connected to the heat source-side unit 120 through the liquid-side connection pipe 106 and the gas-side connection pipe 105 and constitutes a portion of the refrigerant circuit 110.

The usage-side unit 130 includes a usage-side heat exchanger 131, a usage-side fan 132, and a usage-side bridge circuit 154.

In the usage-side heat exchanger 131, the liquid side is connected to the liquid-side connection pipe 106, and a gas-side end is connected to the gas-side connection pipe 105. The usage-side heat exchanger 131 is a heat exchanger that functions as an evaporator for the refrigerant at a low pressure in the refrigeration cycle during the cooling operation and functions as a condenser for the refrigerant at a high pressure in the refrigeration cycle during the heating operation.

After the usage-side fan 132 causes the usage-side unit 130 to suck indoor air thereinto and the air exchanges heat with the refrigerant in the usage-side heat exchanger 131, the usage-side fan 132 generates an air flow to discharge the air to outside. The usage-side fan 132 is rotatably driven by an indoor fan motor.

The usage-side bridge circuit 154 includes four connection points and check valves provided between the respective connection points. A refrigerant pipe extending from an inflow side of the usage-side heat exchanger 131, a refrigerant pipe extending from an outflow side of the usage-side heat exchanger 131, a refrigerant pipe connected to an end portion on the usage-side unit 130 side of the liquid-side connection pipe 106, and a refrigerant pipe connected to an end portion on the usage-side unit 130 side of the gas-side connection pipe 105 are connected to the respective connection points of the usage-side bridge circuit 154. A corresponding check valve blocks the refrigerant flow from the inflow side of the usage-side heat exchanger 131 to the liquid-side connection pipe 106, a corresponding check valve blocks the refrigerant flow from the inflow side of the usage-side heat exchanger 131 to the gas-side connection pipe 105, a corresponding check valve blocks the refrigerant flow from the liquid-side connection pipe 106 to the outflow side of the usage-side heat exchanger 131, and a corresponding check valve blocks the refrigerant flow from the gas-side connection pipe 105 to the outflow side of the usage-side heat exchanger 131.

In FIG. 8G, the air flow formed by the usage-side fan 132 is indicated by dotted arrows. Here, in both cases in which the usage-side heat exchanger 131 of the usage-side unit 130 including the usage-side bridge circuit 154 functions as an evaporator for the refrigerant and functions as a condenser for the refrigerant, the usage-side heat exchanger 131 is configured so that a point (on the downstream side of the air flow) into which the refrigerant flows at the usage-side heat exchanger 131 is the same, a point (on the upstream side of the air flow) at which the refrigerant flows out from the usage-side heat exchanger 131 is the same, and the direction in which the refrigerant flows in the usage-side heat exchanger 131 is the same. Therefore, in both cases in which the usage-side heat exchanger 131 functions as an evaporator for the refrigerant and in which the usage-side heat exchanger 131 functions as a condenser for the refrigerant, the flow direction of the refrigerant that flows in the usage-side heat exchanger 131 is to be opposite to the direction of the air flow formed by the usage-side fan 132 (counter flow at all the time).

The usage-side unit 130 includes the usage-side unit control section 134 that controls the operation of each component constituting the usage-side unit 130. The usage-side unit control section 134 includes a microcomputer including a CPU, memory, and the like. The usage-side unit control section 134 is connected to the heat source-side unit control section 127 through the communication line and sends and receives control signals or the like.

A target-space air temperature sensor 172, an inflow-side heat-exchanger temperature sensor 181, an outflow-side heat-exchanger temperature sensor 183, and the like are provided in the usage-side unit 130. Each sensor is electrically coupled to the usage-side unit control section 134 and sends a detection signal to the usage-side unit control section 134. The target-space air temperature sensor 172 detects the temperature of the air in the target space before the air passes through the usage-side heat exchanger 131. The inflow-side heat-exchanger temperature sensor 181 detects the temperature of the refrigerant before the refrigerant flows into the usage-side heat exchanger 131. The outflow-side heat-exchanger temperature sensor 183 detects the temperature of the refrigerant that flows out from the usage-side heat exchanger 131.

(22-1-2-3) Details of Controller

In the air conditioning apparatus 100, the controller 107 that controls the operations of the air conditioning apparatus 100 is configured by connecting the heat source-side unit control section 127 to the usage-side unit control section 134 through the communication line.

The controller 107 includes mainly a CPU (central processing unit) and memory such as ROM and RAM. Various processes and control operations performed by the controller 107 are realized by causing the components included in the heat source-side unit control section 127 and/or the usage-side unit control section 134 to function as an integral whole.

(22-1-2-4) Operation Modes

Hereinafter, operation modes will be described.

As operation modes, a cooling operation mode and a heating operation mode are provided.

The controller 107 determines one of the cooling operation mode and the heating operation mode to perform based on an instruction received from the remote controller or the like and performs the mode.

(A) Cooling Operation Mode

In the air conditioning apparatus 100, in the cooling operation mode, a connection state of the flow path switching mechanism 122 is to be a cooling-operation connection state in which the discharge side of the compressor 121 is connected to the heat source-side heat exchanger 123 and the suction side of the compressor 121 is connected to the gas-side shutoff valve 128, and the refrigerant filled in the refrigerant circuit 110 is circulated in mainly the order of the compressor 121, the heat source-side heat exchanger 123, the heat source-side expansion mechanism 124, and the usage-side heat exchanger 131.

Specifically, operation frequency is capacity-controlled in the compressor 121 so that, for example, the evaporation temperature of the refrigerant in the refrigerant circuit 110 becomes a target evaporation temperature that is determined in accordance with the difference between a set temperature and an indoor temperature (a temperature detected by the target-space air temperature sensor 172).

The gas refrigerant that has been discharged from the compressor 121, after passing the flow path switching mechanism 122, condenses in the heat source-side heat exchanger 123. In the heat source-side heat exchanger 123, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125. In other words, during the operation of the air conditioning apparatus 100 using the heat source-side heat exchanger 123 as a condenser, in the heat source-side heat exchanger 123, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has flowed through the heat source-side heat exchanger 123 passes through a portion of the heat source-side bridge circuit 153 and is decompressed in the heat source-side expansion mechanism 124 to a low pressure in the refrigeration cycle.

Here, the valve opening degree is controlled in the heat source-side expansion mechanism 124 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of superheating of the refrigerant that flows on a gas side of the usage-side heat exchanger 131 or the degree of superheating of the refrigerant that is sucked by the compressor 121 becomes a target value. Here, the degree of superheating of the refrigerant that flows on the gas side of the usage-side heat exchanger 131 may be obtained by, for example, subtracting the saturation temperature of the refrigerant that corresponds to the temperature detected by the suction pressure sensor 163 from the temperature detected by the outflow-side heat-exchanger temperature sensor 183. A method for controlling the valve opening degree in the heat source-side expansion mechanism 124 is not limited, and, for example, the discharge temperature of the refrigerant that is discharged from the compressor 121 may be controlled to a predetermined temperature, or the degree of superheating of the refrigerant that is discharged from the compressor 121 may be controlled to satisfy a predetermined condition.

In the heat source-side expansion mechanism 124, the refrigerant that has been decompressed to a low pressure in the refrigeration cycle flows into the usage-side unit 130 through the liquid-side shutoff valve 129 and the liquid-side connection pipe 106 and evaporates in the usage-side heat exchanger 131. In the usage-side heat exchanger 131, the refrigerant flows in a direction opposite to the direction of the air flow formed by the usage-side fan 132. In other words, during the operation of the air conditioning apparatus 100 using the usage-side heat exchanger 131 as an evaporator, in the usage-side heat exchanger 131, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has flowed through the usage-side heat exchanger 131, after flowing through the gas-side connection pipe 105, passes through the gas-side shutoff valve 128, the flow path switching mechanism 122, and the low-pressure receiver 141 and is sucked by the compressor 121 again. The liquid refrigerant that cannot be evaporated in the usage-side heat exchanger 131 is stored in the low-pressure receiver 141 as surplus refrigerant.

(B) Heating Operation Mode

In the air conditioning apparatus 100, in the heating operation mode, the connection state of the flow path switching mechanism 122 is to be a heating-operation connection state in which the discharge side of the compressor 121 is connected to the gas-side shutoff valve 128 and the suction side of the compressor 121 is connected to the heat source-side heat exchanger 123, and the refrigerant filled in the refrigerant circuit 110 is circulated in mainly the order of the compressor 121, the usage-side heat exchanger 131, the heat source-side expansion mechanism 124, and the heat source-side heat exchanger 123.

More specifically, in the heating operation mode, operation frequency is capacity-controlled in the compressor 121 so that, for example, the condensation temperature of the refrigerant in the refrigerant circuit 110 is to be a target condensation temperature that is determined in accordance with the difference between a set temperature and an indoor temperature (a temperature detected by the target-space air temperature sensor 172).

The gas refrigerant that has been discharged from the compressor 121, after flowing through the flow path switching mechanism 122 and the gas-side connection pipe 105, flows into a gas-side end of the usage-side heat exchanger 131 of the usage-side unit 130 and condenses in the usage-side heat exchanger 131. In the usage-side heat exchanger 131, the refrigerant flows in a direction opposite to the direction of the air flow formed by the usage-side fan 132. In other words, during the operation of the air conditioning apparatus 100 using the usage-side heat exchanger 131 as a condenser, in the usage-side heat exchanger 131, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has flowed out from a liquid-side end of the usage-side heat exchanger 131 passes through the liquid-side connection pipe 106, flows into the heat source-side unit 120, passes through the liquid-side shutoff valve 129, and is decompressed in the heat source-side expansion mechanism 124 to a low pressure in the refrigeration cycle.

Here, the valve opening degree is controlled in the heat source-side expansion mechanism 124 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of superheating of the refrigerant that is sucked by the compressor 121 becomes a target value. A method for controlling the valve opening degree in the heat source-side expansion mechanism 124 is not limited, and, for example, the discharge temperature of the refrigerant that is discharged from the compressor 121 may be controlled to a predetermined temperature, or the degree of superheating of the refrigerant that is discharged from the compressor 121 may be controlled to satisfy a predetermined condition.

The refrigerant that has been decompressed in the heat source-side expansion mechanism 124 evaporates in the heat source-side heat exchanger 123. In the heat source-side heat exchanger 123, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125. In other words, during the operation of the air conditioning apparatus 100 using the heat source-side heat exchanger 123 as an evaporator, in the heat source-side heat exchanger 123, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has been evaporated in the heat source-side heat exchanger 123 passes through the flow path switching mechanism 122 and the low-pressure receiver 141 and is sucked by the compressor 121 again. The liquid refrigerant that cannot be evaporated in the heat source-side heat exchanger 123 is stored in the low-pressure receiver 141 as surplus refrigerant.

(22-1-2-5) Features of Air Conditioning Apparatus 100

The air conditioning apparatus 100 can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene; thus, the refrigeration cycle is enabled with a refrigerant having a low GWP.

In addition, occurrence of liquid compression can be suppressed in the air conditioning apparatus 100 by providing the low-pressure receiver 141 and without performing control (control of the heat source-side expansion mechanism 124) by which the degree of superheating of the refrigerant that is sucked by the compressor 121 is ensured to be more than or equal to a predetermined value. Therefore, regarding the control of the heat source-side expansion mechanism 124, the heat source-side heat exchanger 123 that is to function as a condenser (the same applies to the usage-side heat exchanger 131 that is to function as a condenser) can be controlled to sufficiently ensure the degree of subcooling of the refrigerant that passes through the exit.

In addition, during both cooling operation and heating operation, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125 (counter flow) in the heat source-side heat exchanger 123. Therefore, when the heat source-side heat exchanger 123 functions as an evaporator, the temperature of the refrigerant that passes therethrough tends to be higher on the exit side than the temperature thereof on the entrance side. Even in such a case, the air flow formed by the heat source-side fan 125 is in a direction opposite to the refrigerant flow; thus, a temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in the heat source-side heat exchanger 123. In addition, when the heat source-side heat exchanger 123 functions as a condenser, the temperature of the refrigerant that passes therethrough tends to be lower on the exit side than the temperature thereof on the entrance side. Even in such a case, the air flow formed by the heat source-side fan 125 is in a direction opposite to the refrigerant flow; thus, the temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in the heat source-side heat exchanger 123.

In addition, during both cooling operation and heating operation, the refrigerant flows in a direction opposite to the direction of the air flow formed by the usage-side fan 132 (counter flow) in the usage-side heat exchanger 131. Therefore, when the usage-side heat exchanger 131 functions as an evaporator for the refrigerant, the temperature of the refrigerant that passes therethrough tends to be higher on the exit side than the temperature thereof on the entrance side. Even in such a case, the air flow formed by the usage-side fan 132 is in a direction opposite to the refrigerant flow; thus, a temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in the usage-side heat exchanger 131. When the usage-side heat exchanger 131 functions as a condenser, the temperature of the refrigerant that passes therethrough tends to be lower on the exit side than the temperature thereof on the entrance side. Even in such a case, the air flow formed by the usage-side fan 132 is in a direction opposite to the refrigerant flow; thus, the temperature difference between the air and the refrigerant is easily sufficiently ensured on both the entrance side and the exit side of the refrigerant in the usage-side heat exchanger 131.

Therefore, even when temperature glide occurs in the evaporator and in the condenser due to the use of a non-azeotropic refrigerant mixture as a refrigerant, in both cooling operation and heating operation, it is possible to sufficiently deliver performance in both the heat exchanger functioning as an evaporator and the heat exchanger functioning as a condenser.

(22-1-3) Third Embodiment

Hereinafter, an air conditioning apparatus 100 a as a refrigeration cycle apparatus according to a third embodiment will be described with reference to FIG. 8I, which is a schematic structural diagram of a refrigerant circuit, and FIG. 8J, which is a schematic control block structural diagram. The air conditioning apparatus 100 a of the third embodiment shares many common features with the air conditioning apparatus 100 of the second embodiment; thus, differences from the air conditioning apparatus 100 of the first embodiment will be mainly described hereinafter.

(22-1-3-1) Configuration of Air Conditioning Apparatus

The air conditioning apparatus 100 a differs from the air conditioning apparatus 100 of the above-described second embodiment mainly in that a bypass pipe 140 having a bypass expansion valve 149 is provided in the heat source-side unit 120, in that a plurality of indoor units (a first usage-side unit 130 and a second usage-side unit 135) are arranged in parallel, and in that an indoor expansion valve is provided on a liquid refrigerant side of the indoor heat exchanger in each indoor unit. In the following description of the air conditioning apparatus 100 a, constituents that are the same as or similar to those of the air conditioning apparatus 100 are given the same references as those given for the air conditioning apparatus 100.

The bypass pipe 140 included in the heat source-side unit 120 is a refrigerant pipe that connects a portion of the refrigerant circuit 110 between the heat source-side expansion mechanism 124 and the liquid-side shutoff valve 129 with a refrigerant pipe extending from one of the connection ports of the flow path switching mechanism 122 to the low-pressure receiver 141. The bypass expansion valve 149 is preferably, but is not limited to, an electrically powered expansion valve whose valve opening degree can be regulated.

As with the above-described embodiment, the first usage-side unit 130 includes a first usage-side heat exchanger 131, a first usage-side fan 132, and a first usage-side bridge circuit 154, and, other than the components, further includes a first usage-side expansion mechanism 133. The first usage-side bridge circuit 154 includes four connection points and check valves provided between the respective connection points. A refrigerant pipe extending from a liquid side of the first usage-side heat exchanger 131, a refrigerant pipe extending from a gas side of the first usage-side heat exchanger 131, a refrigerant pipe branching off from the liquid-side connection pipe 106 toward the first usage-side unit 130, and a refrigerant pipe branching off from the gas-side connection pipe 105 toward the first usage-side unit 130 are connected to the respective connection points of the first usage-side bridge circuit 154.

In FIG. 8I, an air flow formed by the first usage-side fan 132 is indicated by dotted arrows. Here, in both cases in which the first usage-side heat exchanger 131 of the first usage-side unit 130 including the first usage-side bridge circuit 154 functions as an evaporator for the refrigerant and functions as a condenser for the refrigerant, the first usage-side heat exchanger 131 is configured so that a point (on the downstream side of the air flow) into which the refrigerant flows at the first usage-side heat exchanger 131 is the same, a point (on the upstream side of the air flow) at which the refrigerant flows out from the first usage-side heat exchanger 131 is the same, and the direction in which the refrigerant flows in the first usage-side heat exchanger 131 is the same. Therefore, in both cases in which the first usage-side heat exchanger 131 functions as an evaporator for the refrigerant and in which the first usage-side heat exchanger 131 functions as a condenser for the refrigerant, the flow direction of the refrigerant that flows in the first usage-side heat exchanger 131 is to be opposite to the direction of the air flow formed by the first usage-side fan 132 (counter flow at all the time). The first usage-side expansion mechanism 133 is provided in the middle of the refrigerant pipe that branches off from the liquid-side connection pipe 106 toward the first usage-side unit 130 (on the liquid refrigerant side of the first usage-side bridge circuit 154). The first usage-side expansion mechanism 133 is preferably an electrically powered expansion valve whose valve opening degree can be regulated. As with the above-described embodiment, a first usage-side unit control section 134 and a first inflow-side heat-exchanger temperature sensor 181, a first target-space air temperature sensor 172, a first outflow-side heat-exchanger temperature sensor 183 and the like that are electrically coupled to the first usage-side unit control section 134 are provided in the first usage-side unit 130.

As with the first usage-side unit 130, the second usage-side unit 135 includes a second usage-side heat exchanger 136, a second usage-side fan 137, a second usage-side expansion mechanism 138, and a second usage-side bridge circuit 155. The second usage-side bridge circuit 155 includes four connection points and check valves provided between the respective connection points. A refrigerant pipe extending from a liquid side of the second usage-side heat exchanger 136, a refrigerant pipe extending from a gas side of the second usage-side heat exchanger 136, a refrigerant pipe branching off from the liquid-side connection pipe 106 toward the second usage-side unit 135, and a refrigerant pipe branching off from the gas-side connection pipe 105 toward the second usage-side unit 135 are connected to the respective connection points of the second usage-side bridge circuit 155. In FIG. 8I, an air flow formed by the second usage-side fan 137 is indicated by dotted arrows. Here, in both cases in which the second usage-side heat exchanger 136 of the second usage-side unit 135 including the second usage-side bridge circuit 155 functions as an evaporator for the refrigerant and functions as a condenser for the refrigerant, the second usage-side heat exchanger 136 is configured so that a point (on the downstream side of the air flow) into which the refrigerant flows at the second usage-side heat exchanger 136 is the same, a point (on the upstream side of the air flow) at which the refrigerant flows out from the second usage-side heat exchanger 136 is the same, and the direction in which the refrigerant flows in the second usage-side heat exchanger 136 is the same. Therefore, in both cases in which the second usage-side heat exchanger 136 functions as an evaporator for the refrigerant and in which the second usage-side heat exchanger 136 functions as a condenser for the refrigerant, the flow direction of the refrigerant that flows in the second usage-side heat exchanger 136 is to be opposite to the direction of the air flow formed by the second usage-side fan 137 (counter flow at all the time). The second usage-side expansion mechanism 138 is provided in the middle of the refrigerant pipe that branches off from the liquid-side connection pipe 106 toward the second usage-side unit 135 (on the liquid refrigerant side of the second usage-side bridge circuit 155). The second usage-side expansion mechanism 138 is preferably an electrically powered expansion valve whose valve opening degree can be regulated. As with the first usage-side unit 130, a second usage-side unit control section 139 and a second inflow-side heat-exchanger temperature sensor 185, a second target-space air temperature sensor 176, a second outflow-side heat-exchanger temperature sensor 187 that are electrically coupled to the second usage-side unit control section 139 are provided in the second usage-side unit 135.

(22-1-3-2) Operation Modes (A) Cooling Operation Mode

In the air conditioning apparatus 100 a, in a cooling operation mode, operation frequency is capacity-controlled in the compressor 121 so that, for example, the evaporation temperature of the refrigerant in the refrigerant circuit 110 becomes a target evaporation temperature. Here, the target evaporation temperature is preferably determined in accordance with one of the usage-side unit 130 and the usage-side unit 135 whose difference between a set temperature and a usage-side temperature is the largest (the usage-side unit under the heaviest load).

The gas refrigerant that has been discharged from the compressor 121, after passing through the flow path switching mechanism 122, condenses in the heat source-side heat exchanger 123. In the heat source-side heat exchanger 123, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125. In other words, during the operation of the air conditioning apparatus 100 a using the heat source-side heat exchanger 123 as a condenser, in the heat source-side heat exchanger 123, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has flowed through the heat source-side heat exchanger 123, after passing through a portion of the heat source-side bridge circuit 153, passes through the heat source-side expansion mechanism 124 that is controlled to be fully opened and then flows into each of the first usage-side unit 130 and the second usage-side unit 135 through the liquid-side shutoff valve 129 and the liquid-side connection pipe 106.

The valve opening degree of the bypass expansion valve 149 of the bypass pipe 140 is controlled in accordance with a generation state of surplus refrigerant. Specifically, the bypass expansion valve 149 is controlled, for example, based on a high pressure that is detected by the discharge pressure sensor 161 and/or the degree of subcooling of the refrigerant that flows on the liquid side of the heat source-side heat exchanger 123. In such a state, the surplus refrigerant, which is a portion of the refrigerant that has passed through the above-described heat source-side expansion mechanism 124, is sent to the low-pressure receiver 141 through the bypass pipe 140.

The refrigerant that has flowed into the first usage-side unit 130 is decompressed in the first usage-side expansion mechanism 133 to a low pressure in the refrigeration cycle. In addition, the refrigerant that has flowed into the second usage-side unit 135 is decompressed in the second usage-side expansion mechanism 138 to a low pressure in the refrigeration cycle.

Here, the valve opening degree is controlled in the first usage-side expansion mechanism 133 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of superheating of the refrigerant that flows on the gas side of the first usage-side heat exchanger 131 or the degree of superheating of the refrigerant that is sucked by the compressor 121 becomes a target value. Here, the degree of superheating of the refrigerant that flows on the gas side of the first usage-side heat exchanger 131 may be obtained, for example, by subtracting the saturation temperature of the refrigerant that corresponds to the temperature detected by the suction pressure sensor 163 from the temperature detected by the first outflow-side heat-exchanger temperature sensor 183. Similarly, the valve opening degree is controlled in the second usage-side expansion mechanism 138 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of superheating of the refrigerant that flows on the gas side of the second usage-side heat exchanger 136 or the degree of superheating of the refrigerant that is sucked by the compressor 121 becomes a target value. Here, the degree of superheating of the refrigerant that flows on the gas side of the second usage-side heat exchanger 136 may be obtained, for example, by subtracting the saturation temperature of the refrigerant that corresponds to the temperature detected by the suction pressure sensor 163 from the temperature detected by the second outflow-side heat-exchanger temperature sensor 187.

The refrigerant that has been decompressed in the first usage-side expansion mechanism 133 passes through a portion of the first usage-side bridge circuit 154, flows into the first usage-side heat exchanger 131, and evaporates in the first usage-side heat exchanger 131. In the first usage-side heat exchanger 131, the refrigerant flows in a direction opposite to the direction of the air flow formed by the first usage-side fan 132. In other words, during the operation of the air conditioning apparatus 100 a using the first usage-side heat exchanger 131 as an evaporator, in the first usage-side heat exchanger 131, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has passed through the first usage-side heat exchanger 131 passes through a portion of the first usage-side bridge circuit 154 and flows to outside the first usage-side unit 130.

Similarly, the refrigerant that has been decompressed in the second usage-side expansion mechanism 138 passes through a portion of the second usage-side bridge circuit 155, flows into the second usage-side heat exchanger 136, and evaporates in the second usage-side heat exchanger 136. In the second usage-side heat exchanger 136, the refrigerant flows in a direction opposite to the direction of the air flow formed by the second usage-side fan 137. In other words, during the operation of the air conditioning apparatus 100 a using the second usage-side heat exchanger 136 as an evaporator, in the second usage-side heat exchanger 136, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has passed through the second usage-side heat exchanger 136 passes through a portion of the second usage-side bridge circuit 155 and flows to outside the second usage-side unit 135. The refrigerant that has flowed out from the first usage-side unit 130 and the refrigerant that has flowed out from the second usage-side unit 135, after merging with each other, flow through the gas-side connection pipe 105, pass through the gas-side shutoff valve 128, the flow path switching mechanism 122, and the low-pressure receiver 141, and are sucked by the compressor 121 again. The liquid refrigerant that cannot be evaporated in the first usage-side heat exchanger 131 and in the second usage-side heat exchanger 136 is stored in the low-pressure receiver 141 as surplus refrigerant.

(B) Heating Operation Mode

In the air conditioning apparatus 100 a, in the heating operation mode, operation frequency is capacity-controlled in the compressor 121 so that, for example, the condensation temperature of the refrigerant in the refrigerant circuit 110 becomes a target condensation temperature. Here, the target condensation temperature is preferably determined in accordance with one of the usage-side unit 130 and the usage-side unit 135 whose difference between a set temperature and a usage-side temperature is the largest (the usage-side unit under the heaviest load).

The gas refrigerant that has been discharged from the compressor 121, after flowing through the flow path switching mechanism 122 and the gas-side connection pipe 105, flows into each of the first usage-side unit 130 and the second usage-side unit 135.

The refrigerant that has flowed into the first usage-side unit 130, after passing through a portion of the first usage-side bridge circuit 154, condenses in the first usage-side heat exchanger 131. In the first usage-side heat exchanger 131, the refrigerant flows in a direction opposite to the direction of the air flow formed by the first usage-side fan 132. In other words, during the operation of the air conditioning apparatus 100 a using the first usage-side heat exchanger 131 as a condenser, in the first usage-side heat exchanger 131, the flow of the refrigerant and the flow of heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has flowed into the second usage-side unit 135, after passing through a portion of the second usage-side bridge circuit 155, condenses in the second usage-side heat exchanger 136. In the second usage-side heat exchanger 136, the refrigerant flows in a direction opposite to the direction of the air flow formed by the second usage-side fan 137. In other words, during the operation of the air conditioning apparatus 100 a using the second usage-side heat exchanger 136 as a condenser, in the second usage-side heat exchanger 136, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows.

The refrigerant that has flowed out from a liquid-side end of the first usage-side heat exchanger 131, after passing through a portion of the first usage-side bridge circuit 154, is decompressed in the first usage-side expansion mechanism 133 to an intermediate pressure in the refrigeration cycle. Similarly, the refrigerant that has flowed out from a liquid-side end of the second usage-side heat exchanger 136, after passing through a portion of the second usage-side bridge circuit 155, is decompressed in the second usage-side expansion mechanism 138 to an intermediate pressure in the refrigeration cycle.

Here, the valve opening degree is controlled in the first usage-side expansion mechanism 133 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of subcooling of the refrigerant that flows on the liquid-side exit of the first usage-side heat exchanger 131 becomes a target value. Here, the degree of subcooling of the refrigerant that flows on the liquid-side exit of the first usage-side heat exchanger 131 may be obtained, for example, by subtracting the saturation temperature of the refrigerant that corresponds to the temperature detected by the discharge pressure sensor 161 from the temperature detected by the first outflow-side heat-exchanger temperature sensor 183. Similarly, the valve opening degree is controlled in the second usage-side expansion mechanism 138 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of subcooling of the refrigerant that flows on the liquid-side exit of the second usage-side heat exchanger 136 becomes a target value. Here, the degree of subcooling of the refrigerant that flows on the liquid-side exit of the second usage-side heat exchanger 136 may be obtained, for example, by subtracting the saturation temperature of the refrigerant that corresponds to the temperature detected by the discharge pressure sensor 161 from the temperature detected by the second outflow-side heat-exchanger temperature sensor 187.

The refrigerant that has passed through the first usage-side expansion mechanism 133 passes through a portion of the first usage-side bridge circuit 154 and flows to outside the first usage-side unit 130. Similarly, the refrigerant that has passed through the second usage-side expansion mechanism 138 passes through a portion of the second usage-side bridge circuit 155 and flows to outside the second usage-side unit 135. The refrigerant that has flowed out from the first usage-side unit 130 and the refrigerant that has flowed out from the second usage-side unit 135, after merging with each other, flow into the heat source-side unit 120 through the liquid-side connection pipe 106.

The refrigerant that has flowed into the heat source-side unit 120 passes through the liquid-side shutoff valve 129 and is decompressed in the heat source-side expansion mechanism 124 to a low pressure in the refrigeration cycle.

The valve opening degree of the bypass expansion valve 149 of the bypass pipe 140 may be controlled in accordance with the generation state of the surplus refrigerant as in the cooling operation or may be controlled to be fully closed.

Here, the valve opening degree is controlled in the heat source-side expansion mechanism 124 so that a predetermined condition is satisfied. Such a condition is that, for example, the degree of superheating of the refrigerant that is sucked by the compressor 121 becomes a target value. A method for controlling the valve opening degree in the heat source-side expansion mechanism 124 is not limited, and, for example, the discharge temperature of the refrigerant that is discharged from the compressor 121 may be controlled to a predetermined temperature, or the degree of superheating of the refrigerant that is discharged from the compressor 121 may be controlled to satisfy a predetermined condition.

The refrigerant that has been decompressed in the heat source-side expansion mechanism 124 evaporates in the heat source-side heat exchanger 123. In the heat source-side heat exchanger 123, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125. In other words, during the operation of the air conditioning apparatus 100 a using the heat source-side heat exchanger 123 as an evaporator, in the heat source-side heat exchanger 123, the flow of the refrigerant and the flow of the heating medium that exchanges heat with the refrigerant are counter flows. The refrigerant that has passed through the heat source-side heat exchanger 123 passes through the flow path switching mechanism 122 and the low-pressure receiver 141 and is sucked by the compressor 121 again. The liquid refrigerant that cannot be evaporated in the heat source-side heat exchanger 123 is stored in the low-pressure receiver 141 as surplus refrigerant.

(22-1-3-3) Features of Air Conditioning Apparatus 100 a

The air conditioning apparatus 100 a can perform the refrigeration cycle using the refrigerant containing 1,2-difluoroethylene; thus, the refrigeration cycle is enabled with a refrigerant having a low GWP.

In addition, in the air conditioning apparatus 100 a, occurrence of liquid compression can be suppressed by providing the low-pressure receiver 141 and without performing control (control of the heat source-side expansion mechanism 124) by which the degree of superheating of the refrigerant that is sucked by the compressor 121 is ensured to be more than or equal to a predetermined value. Further, during the heating operation, it is possible to easily sufficiently deliver performance of the first usage-side heat exchanger 131 and the second usage-side heat exchanger 136 by controlling the degree of subcooling of each of the first usage-side expansion mechanism 133 and the second usage-side expansion mechanism 138.

During both cooling operation and heating operation, in the heat source-side heat exchanger 123, the refrigerant flows in a direction opposite to the direction of the air flow formed by the heat source-side fan 125 (counter flow). In addition, during both cooling operation and heating operation, in the first usage-side heat exchanger 131, the refrigerant flows in a direction opposite to the direction of the air flow formed by the first usage-side fan 132 (counter flow). Similarly, during both cooling operation and heating operation, in the second usage-side heat exchanger 136, the refrigerant flows in a direction opposite to the direction of the air flow formed by the second usage-side fan 137 (counter flow).

Therefore, even when temperature glide occurs in the evaporator and in the condenser due to the use of a non-azeotropic refrigerant mixture as a refrigerant, in both cooling operation and heating operation, it is possible to sufficiently deliver performance in both the heat exchanger functioning as an evaporator and the heat exchanger functioning as a condenser.

(25) Embodiment of the Technique of Twenty-Fifth Group (25-1) First Embodiment

The following describes, with reference to the drawings, a heat load treatment system 100, which is a refrigeration apparatus according to a first embodiment. The following embodiments, which are provided as specific examples, should not be construed as limiting the technical scope and may be altered as appropriate within a range not departing from the spirit thereof. Words such as up, down, left, right, forward (frontside), and rearward (backside) may be hereinafter used to refer to directions. Unless specified otherwise, these directions correspond to directions denoted by arrows in the drawings. The words relevant to the directions are merely used to facilitate the understanding of the embodiments and should not be construed as limiting the ideas presented in the present disclosure.

(25-1-1) Overall Configuration

FIG. 9A is a schematic configuration diagram of the heat load treatment system 100. The heat load treatment system 100 is a system for treating a heat load in an installation environment. In the present embodiment, the heat load treatment system 100 is an air conditioning system that air-conditions a target space.

The heat load treatment system 100 includes mainly a plurality of heat-source-side units 10 (four heat-source-side units 10 in the example concerned), a heat exchanger unit 30, a plurality of use-side units 60 (four use-side units 60 in the example concerned), a plurality of liquid-side connection pipes LP (four liquid-side connection pipes LP in the example concerned), a plurality of gas-side connection pipes GP (four gas-side connection pipes GP in the example concerned), a first heat-medium connection pipe H1, a second heat-medium connection pipe H2, a refrigerant leakage sensor 70, and a controller 80, which controls the operation of the heat load treatment system 100.

In the heat load treatment system 100, a refrigerant circuit RC, through which refrigerant circulates, is formed in such a manner that each of the heat-source-side units 10 is connected to the heat exchanger unit 30 via the corresponding one of the liquid-side connection pipes LP and the corresponding one of the gas-side connection pipes GP. The plurality of heat-source-side units 10 are arranged in parallel, and a plurality of refrigerant circuits RC (four refrigerant circuits RC in the example concerned) are formed in the heat load treatment system 100 accordingly. In other words, the heat load treatment system 100 includes the plurality of refrigerant circuits RC, each of which is constructed of the corresponding one of the plurality of heat-source-side units 10 and the heat exchanger unit 30. The heat load treatment system 100 performs a vapor compression refrigeration cycle in each refrigerant circuit RC.

In the present embodiment, refrigerant sealed in the refrigerant circuits RC is a refrigerant mixture containing 1,2-difluoroethylene and may be any one of the refrigerants A to D mentioned above.

In the heat load treatment system 100, a heat medium circuit HC, through which a heat medium circulates, is formed in such a manner that the heat exchanger unit 30 and the use-side units 60 are connected to each other via the first heat-medium connection pipe H1 and the second heat-medium connection pipe H2. In other words, the heat exchanger unit 30 and the use-side units 60 constitute the heat medium circuit HC in the heat load treatment system 100. When being driven, a pump 36 of the heat exchanger unit 30 causes the heat medium to circulate through the heat medium circuit HC.

In the present embodiment, the heat medium sealed in the heat medium circuit HC is, for example, a liquid medium such as water or brine. Examples of brine include aqueous sodium chloride solution, aqueous calcium chloride solution, aqueous ethylene glycol solution, and aqueous propylene glycol solution. The liquid medium is not limited to these examples and may be selected as appropriate. Specifically, brine is used as the heat medium in the present embodiment.

(25-1-2) Details on Configuration (25-1-2-1) Heat-Source-Side Unit

in the present embodiment, the heat load treatment system 100 includes four heat-source-side units 10 (see FIG. 9A). The four heat-source-side units 10 cool or heat refrigerant, which is in turn used by the heat exchanger unit 30 to cool or heat the liquid medium. The number of the heat-source-side units 10 is not limited to particular values such as four, which is merely given as an example. One, two, three, or five or more heat-source-side units 10 may be included. The internal configuration of one of the four heat-source-side units 10 is illustrated in FIG. 9A, in which the internal configuration of the remaining three heat-source-side units 10 is omitted. Each of the heat-source-side units 10 that are not illustrated in full has the same configuration as the heat-source-side unit 10 that will be described below.

The heat-source-side units 10 are units that use air as a heat source to cool or heat refrigerant. The heat-source-side units 10 are individually connected to the heat exchanger unit 30 via the respective liquid-side connection pipes LP and the respective gas-side connection pipes GP. In other words, the individual heat-source-side units 10 together with the heat exchanger unit 30 are constituent components of the corresponding refrigerant circuits RC. That is, the plurality of refrigerant circuits RC (four refrigerant circuits RC in the example concerned) are formed in the heat load treatment system 100 in such a manner that the respective heat-source-side units 10 (four heat-source-side units 10 in the example concerned) are individually connected to the heat exchanger unit 30. The refrigerant circuits RC are separated from each other and do not communicate with each other.

Although the installation site of the heat-source-side units 10 is not limited, each of the heat-source-side unit 10 may be installed on a roof or in a space around a building. The heat-source-side unit 10 is connected to the heat exchanger unit 30 via the liquid-side connection pipe LP and the gas-side connection pipe GP to form part of the refrigerant circuit RC.

The heat-source-side unit 10 includes mainly, as devices constituting the refrigerant circuit RC, a plurality of refrigerant pipes (a first pipe P1 to an eleventh pipe P11), a compressor 11, an accumulator 12, a four-way switching valve 13, a heat-source-side heat exchanger 14, a subcooler 15, a heat-source-side first control valve 16, a heat-source-side second control valve 17, a liquid-side shutoff valve 18, and a gas-side shutoff valve 19.

The first pipe P1 forms a connection between the gas-side shutoff valve 19 and a first port of the four-way switching valve 13. The second pipe P2 forms a connection between an inlet port of the accumulator 12 and a second port of the four-way switching valve 13. The third pipe P3 forms a connection between an outlet port of the accumulator 12 and an intake port of the compressor 11. The fourth pipe P4 forms a connection between a discharge port of the compressor 11 and a third port of the four-way switching valve 13. The fifth pipe P5 forms a connection between a fourth port of the four-way switching valve 13 and a gas-side inlet-outlet port of the heat-source-side heat exchanger 14. The sixth pipe P6 forms a connection between a liquid-side inlet-outlet port of the heat-source-side heat exchanger 14 and one end of the heat-source-side first control valve 16. The seventh pipe P7 forms a connection between the other end of the heat-source-side first control valve 16 and one end of a main channel 151 in the subcooler 15. The eighth pipe P8 forms a connection between the other end of the main channel 151 in the subcooler 15 and one end of the liquid-side shutoff valve 18.

The ninth pipe P9 forms a connection between one end of the heat-source-side second control valve 17 and a portion of the sixth pipe P6 between its two ends. The tenth pipe P10 forms a connection between the other end of the heat-source-side second control valve 17 and one end of a subchannel 152 in the subcooler 15. The eleventh pipe P11 forms a connection between the other end of the subchannel 152 in the subcooler 15 and an injection port of the compressor 11.

Each of these refrigerant pipes (the pipes P1 to P11) may be practically constructed of a single pipe or a plurality of pipes connected to each other via a joint.

The compressor 11 is a device that compresses low-pressure refrigerant in the refrigeration cycle to a high pressure. In the present embodiment, the compressor 11 has a closed structure in which a rotary-type or scroll-type positive-displacement compression element is driven and rotated by a compressor motor (not illustrated). The operating frequency of the compressor motor may be controlled by an inverter. The capacity of the compressor 11 is thus controllable. Alternatively, the compressor 11 may be a compressor with fixed capacity.

The accumulator 12 is a container provided to eliminate or reduce the possibility that an excessive amount of liquid refrigerant will be sucked into the compressor 11. The accumulator 12 has a predetermined volumetric capacity required to accommodate refrigerant charged into the refrigerant circuit RC.

The four-way switching valve 13 is a channel-switching mechanism for redirecting a flow of refrigerant in the refrigerant circuit RC. The four-way switching valve 13 enables switching between the normal cycle state and the reverse cycle state. When the four-way switching valve 13 is switched to the normal cycle state, the first port (the first pipe P1) communicates with the second port (the second pipe P2), and the third port (the fourth pipe P4) communicates with the fourth port (the fifth pipe P5) (see solid lines in the four-way switching valve 13 illustrated in FIG. 9A). When the four-way switching valve 13 is switched to the reverse cycle state, the first port (the first pipe P1) communicates with the third port (the forth pipe P4), and the second port (the second pipe P2) communicates with the fourth port (the fifth pipe P5) (see broken lines in the four-way switching valve 13 illustrated in FIG. 9A).

The heat-source-side heat exchanger 14 is a heat exchanger that functions as a refrigerant condenser (or radiator) or a refrigerant evaporator. The heat-source-side heat exchanger 14 functions as a refrigerant condenser during normal cycle operation (operation in which the four-way switching valve 13 is in the normal cycle state). The heat-source-side heat exchanger 14 functions as a refrigerant evaporator during reverse cycle operation (operation in which the four-way switching valve 13 is in the reverse cycle state). The heat-source-side heat exchanger 14 includes a plurality of heat transfer tubes and a heat transfer fin (not illustrated). The heat-source-side heat exchanger 14 is configured to enable exchange of heat between refrigerant in the heat transfer tubes and air flowing around the heat transfer tubes or around the heat transfer fin (heat-source-side airflow, which will be described later).

The subcooler 15 is a heat exchanger that transforms incoming refrigerant into liquid refrigerant in a subcooled state. The subcooler 15 is, for example, a double-tube heat exchanger, and the main channel 151 and the subchannel 152 are formed in the subcooler 15. The subcooler 15 is configured to enable exchange of heat between refrigerant flowing through the main channel 151 and refrigerant flowing through the subchannel 152.

The heat-source-side first control valve 16 is an electronic expansion valve whose opening degree is controllable, such that the pressure of incoming refrigerant may be reduced in accordance with the opening degree or the flow rate of incoming refrigerant may be regulated in accordance with the opening degree. The heat-source-side first control valve 16 is capable of switching between the opened state and the closed state. The heat-source-side first control valve 16 is disposed between the heat-source-side heat exchanger 14 and the subcooler 15 (the main channel 151).

The heat-source-side second control valve 17 is an electronic expansion valve whose opening degree is controllable, such that the pressure of incoming refrigerant may be reduced in accordance with the opening degree or the flow rate of incoming refrigerant may be regulated in accordance with the opening degree. The heat-source-side second control valve 17 is capable of switching between the opened state and the closed state. The heat-source-side second control valve 17 is disposed between the heat-source-side heat exchanger 14 and the subcooler 15 (the subchannel 152).

The liquid-side shutoff valve 18 is a manual valve disposed in the portion where the eighth pipe P8 is connected to the liquid-side connection pipe LP. One end of the liquid-side shutoff valve 18 is connected to the eighth pipe P8, and the other end of the liquid-side shutoff valve 18 is connected to the liquid-side connection pipe LP.

The gas-side shutoff valve 19 is a manual valve disposed in the portion where the first pipe P1 is connected to the gas-side connection pipe GP. One end of the gas-side shutoff valve 19 is connected to the first pipe P1, and the other end of the gas-side shutoff valve 19 is connected to the gas-side connection pipe GP.

The heat-source-side unit 10 also includes a heat-source-side fan 20, which generates heat-source-side airflow flowing through the heat-source-side heat exchanger 14. The heat-source-side fan 20 is a fan that supplies the heat-source-side heat exchanger 14 with the heat-source-side airflow, which is a cooling source or a heating source for refrigerant flowing through the heat-source-side heat exchanger 14. The heat-source-side fan 20 includes, as a drive source, a heat-source-side fan motor (not illustrated), which executes on-off control and regulates the revolution frequency as circumstances demand.

In addition, the heat-source-side unit 10 includes a plurality of heat-source-side sensors S1 (see FIG. 9C) to sense the state (the pressure or temperature in particular) of refrigerant in the refrigerant circuit RC. Each heat-source-side sensor S1 is a pressure sensor or a temperature sensor such as a thermistor or a thermocouple. A first temperature sensor 21, which senses the temperature (suction temperature) of refrigerant on the intake side of the compressor 11 (refrigerant in the third pipe P3), and/or a second temperature sensor 22, which senses the temperature (discharge temperature) of refrigerant on the discharge side of the compressor 11 (refrigerant in the fourth pipe P4) may be included as the heat-source-side sensor S1. A third temperature sensor 23, which senses the temperature of refrigerant on the liquid side of the heat-source-side heat exchanger 14 (refrigerant in the sixth pipe P6), a fourth temperature sensor 24, which senses the temperature of refrigerant in the eighth pipe P8, and/or a fifth temperature sensor 25, which senses the temperature of refrigerant in the eleventh pipe P11 may be included as the heat-source-side sensor S1. A first pressure sensor 27, which senses the pressure (intake pressure) of refrigerant on the intake side of the compressor 11 (refrigerant in the second pipe P2), and/or a second pressure sensor 28, which senses the pressure (discharge pressure) on the discharge side of the compressor 11 (refrigerant in the fourth pipe P4) may be included as the heat-source-side sensor S1.

The heat-source-side unit 10 also includes a heat-source-side unit control unit 29, which controls the operation and states of the devices included in the heat-source-side unit 10. For example, various electric circuits, a microprocessor, and a microcomputer including a memory chip that stores programs to be executed by the microprocessor are included in the heat-source-side unit control unit 29, which can thus perform its functions. The heat-source-side unit control unit 29 is electrically connected to the devices (11, 13, 16, 17, 20) and the heat-source-side sensors S1 of the heat-source-side unit 10 to perform signal input and output. The heat-source-side unit control unit 29 is electrically connected through a communication line to a heat exchanger unit control unit 49 (which will be described later) of the heat exchanger unit 30 to transmit and receive control signals.

(25-1-2-2) Heat Exchanger Unit

The heat exchanger unit 30 is a device in which a heat medium is cooled and/or heated by exchanging heat with refrigerant. In the present embodiment, cooling of the heat medium and heating of the heat medium are performed in the heat exchanger unit 30 in such a manner that heat is exchanged between the heat medium and refrigerant. The heat medium cooled or heated by the liquid refrigerant in the heat exchanger unit 30 is transferred to the use-side units 60.

The heat exchanger unit 30 is a unit in which a heat medium that is to be transferred to the use-side units 60 is cooled or heated by exchanging heat with the refrigerant. Although the installation site of the heat exchanger unit 30 is not limited, the heat exchanger unit 30 may be installed indoors (e.g., in an equipment/device room). As constituent devices of the refrigerant circuits RC, refrigerant pipes (refrigerant pipes Pa, Pb, Pc, and Pd), expansion valves 31, and on-off valves 32 are included in the heat exchanger unit 30. The number of the refrigerant pipes is the same as the number of the heat-source-side units 10 (the refrigerant circuits RC); that is, the number of the refrigerant pipes is equal to four in the example concerned. The same holds for the number of the expansion valves 31 and the number of the on-off valves 32. As a constituent device of the refrigerant circuits RC and of the heat medium circuit HC, a heat exchanger 33 is included in the heat exchanger unit 30.

The refrigerant pipe Pa forms a connection between the liquid-side connection pipe LP and one end of the expansion valve 31. The refrigerant pipe Pb forms a connection between the other end of the expansion valve 31 and a liquid-side refrigerant inlet-outlet port of the heat exchanger 33. The refrigerant pipe Pc forms a connection between a gas-side refrigerant inlet-outlet port of the heat exchanger 33 and one end of the on-off valve 32. The refrigerant pipe Pd forms a connection between the other end of the on-off valve 32 and the gas-side connection pipe GP. Each of these refrigerant pipes (the pipes Pa to Pd) may be practically constructed of a single pipe or a plurality of pipes connected to each other via a joint.

The expansion valve 31 is an electronic expansion valve whose opening degree is controllable, such that the pressure of incoming refrigerant may be reduced in accordance with the opening degree or the flow rate of incoming refrigerant may be regulated in accordance with the opening degree. The expansion valve 31 is capable of switching between the opened state and the closed state. The expansion valve 31 is disposed between the heat exchanger 33 and the liquid-side connection pipe LP.

The on-off valve 32 is a control valve capable of switching between the opened state and the closed state. The on-off valve 32 in the closed state interrupts refrigerant. The on-off valve 32 is disposed between the heat exchanger 33 and the gas-side connection pipe GP.

A plurality of paths (refrigerant paths RP) for refrigerant flowing through the refrigerant circuits RC are formed in heat exchanger 33. In the heat exchanger 33, the refrigerant paths RP do not communicate with each other. On this account, each refrigerant path RP has a liquid-side inlet-outlet port and a gas-side inlet-outlet port. The number of liquid-side inlet-outlet ports in the heat exchanger 33 is the same as the number of refrigerant paths RP; that is, the number of liquid-side inlet-outlet ports in the heat exchanger 33 is equal to four in the example concerned. The same holds for the number of gas-side inlet-outlet ports in the heat exchanger 33. A path (heat medium path HP) for the heat medium flowing through the heat medium circuit HC is also formed in the heat exchanger 33.

More specifically, a first heat exchanger 34 and a second heat exchanger 35 are included as the heat exchanger 33. The first heat exchanger 34 and the second heat exchanger 35 are discrete devices. Two separate refrigerant paths RP are formed in each of the first heat exchanger 34 and the second heat exchanger 35. The first heat exchanger 34 and the second heat exchanger 35 are configured as follows: one end of each refrigerant path RP is connected to the refrigerant pipe Pb of the corresponding one of the refrigerant circuits RC, and the other end of each refrigerant path RP is connected to the refrigerant pipe Pc of the corresponding one of the refrigerant circuits RC. In the first heat exchanger 34, one end of the heat medium path HP is connected to a heat medium pipe Hb, which will be described later, and the other end of the heat medium path HP is connected to a heat medium pipe Hc, which will be described later. In the second heat exchanger 35, one end of the heat medium path HP is connected to Hc, which will be described later, and the other end of the heat medium path HP is connected to a heat medium pipe Hd, which will be described later. In the heat medium circuit HC, the heat medium path HP of the first heat exchanger 34 and the heat medium path HP of the second heat exchanger 35 are arranged in series. Each of the first heat exchanger 34 and the second heat exchanger 35 is configured to enable exchange of heat between refrigerant flowing through the refrigerant paths RP (the refrigerant circuits RC) and the heat medium flowing through the heat medium path HP (the heat medium circuit HC).

As a constituent device of the heat medium circuit HC, heat medium pipes (heat medium pipes Ha, Hb, Hc, and Hd) and the pump 36 are also included in the heat exchanger unit 30.

One end of the heat medium pipe Ha is connected to the first heat-medium connection pipe H1, and the other end of the heat medium pipe Ha is connected to an intake-side port of the pump 36. One end of the heat medium pipe Hb is connected to a discharge-side port of the pump 36, and the other end of the heat medium pipe Hb is connected to one end of the heat medium path HP of the first heat exchanger 34. One end of the heat medium pipe He is connected to the other end of the heat medium path HP of the first heat exchanger 34, and the other end of the heat medium pipe Hc is connected to one end of the heat medium path HP of the second heat exchanger 35. One end of the heat medium pipe Hd is connected to the other end of the heat medium path HP of the second heat exchanger 35, and the other end of the heat medium pipe Hd is connected to the second heat-medium connection pipe H2. Each of these heat medium pipes (the pipes Ha to Hd) may be practically constructed of a single pipe or a plurality of pipes connected to each other via a joint.

The pump 36 is disposed in the heat medium circuit HC. During operation, the pump 36 sucks in and discharges the heat medium. The pump 36 includes a motor that is a drive source. The motor is inverter-controlled, and the revolution frequency is regulated accordingly. The discharge flow rate of the pump 36 is thus variable. The heat exchanger unit 30 may include a plurality of pumps 36 connected in series or parallel in the heat medium circuit HC. The pump 36 may be a metering pump.

The heat exchanger unit 30 includes a plurality of heat exchanger unit sensors S2 (see FIG. 9C) to sense the state (the pressure or temperature in particular) of refrigerant in the refrigerant circuits RC. Each heat exchanger unit sensor S2 is a pressure sensor or a temperature sensor such as a thermistor or a thermocouple. A sixth temperature sensor 41, which senses the temperature of refrigerant on the liquid side of the heat exchanger 33 (refrigerant in the refrigerant pipe Pb on the refrigerant path RP), and/or a seventh temperature sensor 42, which senses the temperature of refrigerant on the gas-side of the heat exchanger 33 (refrigerant in the refrigerant pipe Pc on the refrigerant path RP) may be included as the heat exchanger unit sensor S2. A third pressure sensor 43, which senses the pressure of refrigerant on the liquid side of the heat exchanger 33 (refrigerant in the refrigerant pipe Pb on the refrigerant path RP), and/or a fourth pressure sensor 44, which senses the pressure on the gas-side of the heat exchanger 33 (refrigerant in the refrigerant pipe Pc on the refrigerant path RP) may be included as the heat exchanger unit sensor S2.

The heat exchanger unit 30 includes an exhaust fan unit to enable the heat exchanger unit 30 to discharge leakage refrigerant at the time of occurrence of refrigerant leakage in the heat exchanger unit 30 (the refrigerant circuit RC). The exhaust fan unit includes an exhaust fan 46. The exhaust fan 46 is driven along with a drive source (e.g., a fan motor). When being driven, the exhaust fan 46 generates a first airflow AF1, which flows out of the heat exchanger unit 30. The exhaust fan 46 is not limited to a particular type of fan and is, for example, a sirocco fan or a propeller fan.

The heat exchanger unit 30 also includes a cooling fan 48. The cooling fan 48 is driven along with a drive source (e.g., a fan motor). When being driven, the cooling fan 48 generates a second airflow AF2 to cool electric components (heating components) disposed in the heat exchanger unit 30. The cooling fan 48 is disposed in such a manner that the second airflow AF2 flows around the heating components to perform heat exchange and then flows out of the heat exchanger unit 30. The cooling fan 48 is not limited to a particular type of fan and is, for example, a sirocco fan or a propeller fan.

The heat exchanger unit 30 also includes a heat exchanger unit control unit 49, which controls the operation and states of the devices included in the heat exchanger unit 30. For example, a microprocessor, a microcomputer including a memory chip that stores programs to be executed by the microprocessor, and various electric components are included in the heat exchanger unit control unit 49, which can thus perform its functions. The heat exchanger unit control unit 49 is electrically connected to the devices and the heat exchanger unit sensors S2 of the heat exchanger unit 30 to perform signal input and output. The heat exchanger unit control unit 49 is electrically connected through a communication line to a heat-source-side unit control unit 29, control units (not illustrated) disposed in the corresponding use-side units 60, or a remote control (not illustrated) to transmit and receive control signals. The electric components included in the heat exchanger unit control unit 49 are cooled by the second airflow AF2 generated by the cooling fan 48.

(25-1-2-3) Use-Side Unit

Each use-side unit 60 is equipment that uses the heat medium cooled or heated in the heat exchanger unit 30. The individual use-side units 60 are connected to the heat exchanger unit 30 via, for example, the first heat-medium connection pipe H1 and the second heat-medium connection pipe H2. The individual use-side units 60 and the heat exchanger unit 30 constitute the heat medium circuit HC.

In the present embodiment, each use-side unit 60 is an air handling unit or a fan coil unit that performs air conditioning through exchange of heat between the heat medium cooled or heated in the heat exchanger unit 30 and air.

Only one use-side unit 60 is illustrated in FIG. 9A. Nevertheless, the heat load treatment system 100 may include a plurality of use-side units, and the heat medium cooled or heated in the heat exchanger unit 30 may branch out to be transferred to the individual use-side units. The use-side units that may be included in the heat load treatment system 100 may be of the same type. Alternatively, more than one type of equipment may be included as the use-side units.

(25-1-2-4) Liquid-Side Connection Pipe and Gas-Side Connection Pipe

The liquid-side connection pipes LP and the gas-side connection pipes GP form refrigerant paths in such a manner as to connect the heat exchanger unit 30 to the corresponding heat-source-side units 10. The liquid-side connection pipes LP and the gas-side connection pipes GP are installed on-site. Each of the liquid-side connection pipes LP and the gas-side connection pipes GP may be practically constructed of a single pipe or a plurality of pipes connected to each other via a joint.

(25-1-2-5) First Heat-Medium Connection Pipe and Second Heat-Medium Connection Pipe

The first heat-medium connection pipe H1 and the second heat-medium connection pipe H2 form heating medium paths in such a manner as to connect the heat exchanger unit 30 to the corresponding use-side units 60. The first heat-medium connection pipe H1 and the second heat-medium connection pipe H2 are installed on-site. Each of the first heat-medium connection pipe H1 and the second heat-medium connection pipe H2 may be practically constructed of a single pipe or a plurality of pipes connected to each other via a joint.

(25-1-2-6) Refrigerant Leakage Sensor

The refrigerant leakage sensor 70 is a sensor for sensing leakage of refrigerant in the space in which the heat exchanger unit 30 is installed (an equipment/device room R, which will be described later). More specifically, the refrigerant leakage sensor 70 is configured to sense leakage refrigerant in the heat exchanger unit 30. In the example concerned, the refrigerant leakage sensor 70 is a well-known general-purpose product suited to the type of refrigerant sealed in the refrigerant circuits RC. The refrigerant leakage sensor 70 is disposed in the space in which the heat exchanger unit 30 is installed. In the present embodiment, the refrigerant leakage sensor 70 is disposed in the heat exchanger unit 30.

The refrigerant leakage sensor 70 continuously or intermittently outputs, to the controller 80, electrical signals (refrigerant-leakage-sensor detection signals) corresponding to detection values. More specifically, the refrigerant-leakage-sensor detection signals output by the refrigerant leakage sensor 70 vary in voltage depending on the concentration of refrigerant sensed by the refrigerant leakage sensor 70. In other words, the refrigerant-leakage-sensor detection signals are output to the controller 80 in a manner so as to enable not only a determination on whether leakage of refrigerant has occurred in the refrigerant circuit RC but also a determination of the concentration of leakage refrigerant in the space in which the refrigerant leakage sensor 70 is installed, or more specifically, the concentration of refrigerant sensed by the refrigerant leakage sensor 70.

(25-1-2-7) Controller

The controller 80 illustrated in FIG. 9C is a computer that controls the states of the individual devices to control the operation of the heat load treatment system 100. In the present embodiment, the controller 80 is configured in such a manner that the heat-source-side unit control unit 29, the heat exchanger unit control unit 49, and devices connected to these units (e.g., control units disposed in the corresponding use-side units and a remote control) are connected to each other through communication lines. In the present embodiment, the heat-source-side unit control unit 29, the heat exchanger unit control unit 49, and the devices connected to these units cooperate to serve as the controller 80.

(25-1-3) Installation Layout of Heat Load Treatment System

FIG. 9B is a schematic diagram illustrating an installation layout of the heat load treatment system 100. Although the installation site of the heat load treatment system 100 is not limited, the heat load treatment system 100 is installed in, for example, a building, a commercial facility, or a plant. In the present embodiment, the heat load treatment system 100 is installed in a building B1 as illustrated in FIG. 9B. The building B1 has a plurality of floors. The number of floors or rooms in the building B1 may be changed as appropriate.

The building B1 includes the equipment/device room R. The equipment/device room R is a space in which electric equipment, such as a switchboard and a generator, or cooling/heating devices, such as a boiler, are installed. The equipment/device room R is an accessible space in which people can stay. The equipment/device room R is, for example, a basement in which people can walk. In the present embodiment, the equipment/device room R is located on the lowermost floor of the building B1. The building B1 includes a plurality of living spaces SP, each of which is provided for activities of the occupants. In the present embodiment, the living spaces SP are located on the respective floors above the equipment/device room R.

Referring to FIG. 9B, the heat-source-side unit 10 is installed on the rooftop of the building B1. The heat exchanger unit 30 is installed in the equipment/device room R. On this account, the liquid-side connection pipe LP and the gas-side connection pipe GP extend in a vertical direction between the rooftop and the equipment/device room R.

Referring to FIG. 9B, the individual use-side units 60 are disposed in the living spaces SP. On this account, the first heat-medium connection pipe H1 and the second heat-medium connection pipe H2 extend in a vertical direction through the living spaces SP and the equipment/device room R.

The building B1 is equipped with a ventilating apparatus 200, which provides ventilation (forced ventilation or natural ventilation) in the equipment/device room R. The ventilating apparatus 200 is installed in the equipment/device room R. Specifically, a ventilating fan 210 is installed as the ventilating apparatus 200 in the equipment/device room R. The ventilating fan 210 is connected to a plurality of ventilating ducts D. When being driven, the ventilating fan 210 ventilates the equipment/device room R in such a manner that air (room air RA) in the equipment/device room R is discharged as exhaust air EA to the external space and air (outside air OA) in the external space is supplied as supply air SA to the equipment/device room R. The ventilating fan 210 is thus regarded as the ventilating apparatus that provides ventilation in the equipment/device room R. The operation (e.g., on-off or the revolution frequency) of the ventilating fan 210 may be controlled by the controller 80. The ventilating fan 210 is controlled in such a manner as to switch, as appropriate, between an intermittent operation mode in which the ventilating fan 210 operates intermittently and a continuous operation mode in which the ventilating fan 210 operates continuously.

In the equipment/device room R, an open-close mechanism 220 is also installed as the ventilating apparatus 200. The open-close mechanism 220 is a mechanism capable of switching between an opened state in which the equipment/device room R communicates with another space (e.g., the external space) and a closed state in which the equipment/device room R is shielded. That is, the open-close mechanism 220 opens or closes a vent through which the equipment/device room R communicates with another space. The open-close mechanism 220 is, for example, a door, a hatch, a window, or a shutter, the opening and closing of which are controllable. The open-close mechanism 220 is electrically connected to the controller 80 through an adapter 80 b (see FIG. 9C). The state (the opened state or the closed state) of the ventilating fan 210 is controlled by the controller 80.

(25-1-4) Features

The refrigerant mixture that is any one of the refrigerants A to D mentioned above is used as refrigerant sealed in the refrigerant circuits RC serving as a first cycle in the heat load treatment system 100 according to the present embodiment, where the efficiency of heat exchange in the heat exchanger unit 30 is enhanced accordingly.

(25-2) Second Embodiment

FIG. 9D is a diagram illustrating a refrigerant circuit included in a two-stage refrigeration apparatus 500, which is a refrigeration apparatus according to the present embodiment. The two-stage refrigeration apparatus 500 includes a first cycle 510, which is a high-stage-side refrigeration cycle on the high temperature side, and a second cycle 520, which is a low-stage-side refrigeration cycle on the low temperature side. The first cycle 510 and the second cycle 520 are thermally connected to each other through a cascade condenser 531. Constituent elements of the first cycle 510 and the constituent elements of the second cycle 520 are accommodated in an outdoor unit 501 or a cooling unit 502, which will be described later.

With consideration given to possible refrigerant leakage, carbon dioxide (CO₂), which does not have a significant impact on global warming, is used as refrigerant sealed in the second cycle 520. Refrigerant sealed in the first cycle 510 is a refrigerant mixture containing 1,2-difluoroethylene and may be any one of the refrigerants A to D mentioned above. The low-temperature-side refrigerant sealed in the second cycle 520 is referred to as a second refrigerant, and the high-temperature-side refrigerant sealed in the first cycle 510 is referred to as a first refrigerant.

The first cycle 510 is a refrigeration cycle through which the first refrigerant circulates. A refrigerant circuit is formed in the first cycle 510 in such a manner that a first compressor 511, a first condenser 512, a first expansion valve 513, and a first evaporator 514 are serially connected to each other via a refrigerant pipe. The refrigerant circuit provided in the first cycle 510 is herein referred to as a first refrigerant circuit.

The second cycle 520 is a refrigeration cycle through which the second refrigerant circulates. A refrigerant circuit is formed in the second cycle 520 in such a manner that a second compressor 521, a second upstream-side condenser 522, a second downstream-side condenser 523, a liquid receiver 525, a second downstream-side expansion valve 526, and a second evaporator 527 are serially connected to each other via a refrigerant pipe. The second cycle 520 includes a second upstream-side expansion valve 524, which is disposed between the second downstream-side condenser 523 and the liquid receiver 525. The refrigerant circuit provided in the second cycle 520 is herein referred to as a second refrigerant circuit.

The two-stage refrigeration apparatus 500 includes the cascade condenser 531 mentioned above. The cascade condenser 531 is configured in such a manner that the first evaporator 514 and the second downstream-side condenser 523 are coupled to each other to enable exchange of heat between refrigerant flowing through the first evaporator 514 and refrigerant flowing through the second downstream-side condenser 523. The cascade condenser 531 is thus regarded as a refrigerant heat exchanger. With the cascade condenser 531 being provided, the second refrigerant circuit and the first refrigerant circuit constitute a multistage configuration.

The first compressor 511 sucks in the first refrigerant flowing through the first refrigerant circuit, compresses the first refrigerant to transform it into high-temperature, high-pressure gas refrigerant, and then discharges the gas refrigerant. In the present embodiment, the first compressor 511 is a compressor of the type that is capable of adjusting the refrigerant discharge amount through control of the revolution frequency by an inverter circuit.

The first condenser 512 causes, for example, air or brine to exchange heat with refrigerant flowing through the first refrigerant circuit, and in turn, the refrigerant is condensed into a liquid. In the present embodiment, the first condenser 512 enables exchange of heat between outside air and refrigerant. The two-stage refrigeration apparatus 500 includes a first condenser fan 512 a. The first condenser fan 512 a blows outside air into the first condenser 512 to promote heat exchange in the first condenser 512. The airflow rate of the first condenser fan 512 a is adjustable.

The first expansion valve 513 decompresses and expands the first refrigerant flowing through the first refrigerant circuit and is, for example, an electronic expansion valve.

In the first evaporator 514, refrigerant flowing through the first refrigerant circuit evaporates and gasifies as a result of heat exchange. In the present embodiment, the first evaporator 514 includes, for example, a heat transfer tube that allows, in the cascade condenser 531, passage of refrigerant flowing through the first refrigerant circuit. In the cascade condenser 531, heat is exchanged between the first refrigerant flowing through the first evaporator 514 and the second refrigerant flowing through the second refrigerant circuit.

The second compressor 521 sucks in the second refrigerant flowing through the second refrigerant circuit, compresses the second refrigerant to transform it into high-temperature, high-pressure gas refrigerant, and then discharges the gas refrigerant. In the present embodiment, the second compressor 521 is, for example, a compressor of the type that is capable of adjusting the refrigerant discharge amount through control of the revolution frequency by an inverter circuit.

The second upstream-side condenser 522 causes, for example, air or brain to exchange heat with refrigerant flowing through the first refrigerant circuit, and in turn, the refrigerant is condensed into a liquid. In the present embodiment, the second upstream-side condenser 522 enables exchange of heat between outside air and refrigerant. The two-stage refrigeration apparatus 500 includes a second condenser fan 522 a. The second condenser fan 522 a blows outside air into the second upstream-side condenser 522 to promote heat exchange in the second upstream-side condenser 522. The second condenser fan 522 a is a fan whose airflow rate is adjustable.

In the second downstream-side condenser 523, the refrigerant condensed into a liquid in the second upstream-side condenser 522 is further transformed into supercooled refrigerant. In the present embodiment, the second downstream-side condenser 523 includes, for example, a heat transfer tube that allows, in the cascade condenser 531, passage of the second refrigerant flowing through the second refrigerant circuit. In the cascade condenser 531, heat is exchanged between the second refrigerant flowing through the second downstream-side condenser 523 and the first refrigerant flowing through the first refrigerant circuit.

The second upstream-side expansion valve 524 decompresses and expands the second refrigerant flowing through the second refrigerant circuit, and the second upstream-side expansion valve 524 in the example concerned is an electronic expansion valve.

The liquid receiver 525 is disposed downstream of the second downstream-side condenser 523 and the second upstream-side expansion valve 524. The liquid receiver 525 stores refrigerant temporarily.

The second downstream-side expansion valve 526 decompresses and expands the second refrigerant flowing through the second refrigerant circuit and is an electronic expansion valve.

In the second evaporator 527, the first refrigerant flowing through the first refrigerant circuit evaporates and gasifies as a result of heat exchange. Exchange of heat between a cooling target and the refrigerant in the second evaporator 527 results in direct or indirect cooling of the cooling target.

Constituent elements of the two-stage refrigeration apparatus 500 mentioned above are accommodated in the outdoor unit 501 or the cooling unit 502. The cooling unit 502 is used as, for example, a refrigerator-freezer showcase or a unit cooler. The first compressor 511, the first condenser 512, the first expansion valve 513, the first evaporator 514, the second compressor 521, the second upstream-side condenser 522, the second downstream-side condenser 523, the second upstream-side expansion valve 524, the liquid receiver 525, a supercooled refrigerant pipe 528, a vapor refrigerant pipe 529, a capillary tube 528 a, and a check valve 529 a in the present embodiment are accommodated in the outdoor unit 501. The second downstream-side expansion valve 526 and the second evaporator 527 are accommodated in the cooling unit 502. The outdoor unit 501 and the cooling unit 502 are connected to each other via two pipes, namely, a liquid pipe 551 and a gas pipe 552.

With the two-stage refrigeration apparatus 500 being configured as described above, the following describes, in accordance with the flow of refrigerants flowing through the respective refrigerant circuits, the way in which the constituent devices work during normal cooling operation for cooling a cooling target, namely, air.

Referring to FIG. 9D, the first cycle 510 works as follows. The first compressor 511 sucks in the first refrigerant, compresses the first refrigerant to transform it into high-temperature, high-pressure gas refrigerant, and then discharges the gas refrigerant. After being discharged, the first refrigerant flows into the first condenser 512. In the first condenser 512, the outside air supplied by the first condenser fan 512 a exchanges heat with the first refrigerant in the form of gas refrigerant, and the first refrigerant is in turn condensed into a liquid. After being condensed into a liquid, the first refrigerant flows through the first expansion valve 513. The first refrigerant condensed into a liquid is decompressed by the first expansion valve 513. After being decompressed, the first refrigerant flows into the first evaporator 514 included in the cascade condenser 531. In the first evaporator 514, the first refrigerant evaporates and gasifies by exchanging heat with the second refrigerant flowing through the second downstream-side condenser 523. After the evaporation and gasification, the first refrigerant is sucked into the first compressor 511.

Referring to FIG. 9D, the second cycle 520 works as follows. The second compressor 521 sucks in the second refrigerant, compresses the second refrigerant to transform it into high-temperature, high-pressure gas refrigerant, and then discharges the gas refrigerant. After being discharged, the second refrigerant flows into the second upstream-side condenser 522. In the second upstream-side condenser 522, the outside air supplied by the second condenser fan 522 a exchanges heat with the second refrigerant, which is in turn condensed and flows into the second downstream-side condenser 523 included in the cascade condenser 531. In the second downstream-side condenser 523, the first refrigerant is supercooled by exchanging heat with the first refrigerant flowing through the first evaporator 514. The supercooled second refrigerant flows through the second upstream-side expansion valve 524. The supercooled second refrigerant is decompressed by the second upstream-side expansion valve 524 to an intermediate pressure. The second refrigerant decompressed to the intermediate pressure flows through the liquid receiver 525 and is then decompressed to a low pressure while flowing through the second downstream-side expansion valve 526. The second refrigerant decompressed to the low pressure flows into the second evaporator 527. The second evaporator 527 operates a second evaporator fan 527 a so that air in a refrigerated warehouse exchanges heat with the second refrigerant, which in turn evaporates and gasifies. After the evaporation and gasification, the second refrigerant is sucked into the second compressor 521.

The refrigerant mixture that is any one of the refrigerants A to D mentioned above is used as the first refrigerant sealed in the first cycle 510 of the two-stage refrigeration apparatus 500 according to the present embodiment, where the efficiency of heat exchange in the cascade condenser 531 is enhanced accordingly. Using, as the first refrigerant, the refrigerant mixture that is any one of the refrigerant A to D can help achieve a global warming potential (GWP) lower than the GWP achievable through the use of R32.

(25-2-1) First Modification of Second Embodiment

In the embodiment above, the refrigerant mixture that is any one of the refrigerants A to D mentioned above is used as the first refrigerant sealed in the first cycle 510, and carbon dioxide is used as the second refrigerant sealed in the second cycle 520. As with the first refrigerant, the second refrigerant may be the refrigerant mixture that is any one of the refrigerants A to D mentioned above. In the example concerned, the first cycle 510 and the second cycle 520 are coupled to each other via the cascade condenser 531 to constitute the two-stage refrigeration apparatus 500. The amount of refrigerant charged into the cycle (the second cycle 520) extending through the cooling unit 502 may be smaller in the apparatus having this configuration than in a one-stage apparatus. This feature enables a reduction in costs associated with safeguards against possible refrigerant leakage in the cooling unit 502.

(25-2-2) Second Modification of Second Embodiment

In the embodiment above, the refrigerant mixture that is any one of the refrigerants A to D mentioned above is used as the first refrigerant sealed in the first cycle 510, and carbon dioxide is used as the second refrigerant sealed in the second cycle 520. Alternatively, R32 may be used as the first refrigerant, and the refrigerant mixture that is any one of the refrigerants A to D mentioned above may be used as the second refrigerant. Such a refrigerant mixture typically involves a pressure-resistance design value that is lower than the pressure-resistance design value necessitated in the case of using carbon dioxide (CO₂), and the level of pressure resistance required of pipes and components constituting the second cycle 520 may be lowered accordingly.

(25-3) Third Embodiment (25-3-1) Overall Configuration

FIG. 9E illustrates an air-conditioning hot water supply system 600, which is a refrigeration apparatus according to a third embodiment. FIG. 9E is a circuit configuration diagram of the air-conditioning hot water supply system 600. The air-conditioning hot water supply system 600 includes an air conditioning apparatus 610 and a hot water supply apparatus 620. The hot water supply apparatus 620 is connected with a hot-water-supply hot water circuit 640.

(25-3-2) Details on Configuration (25-3-2-1) Air Conditioning Apparatus

The air conditioning apparatus 610 includes an air-conditioning refrigerant circuit 615, with a compressor 611, an outdoor heat exchanger 612, an expansion valve 613, and an indoor heat exchanger 614 being arranged in such a manner as to be connected to the air-conditioning refrigerant circuit 615. Specifically, the discharge side of the compressor 611 is connected with a first port P1 of a four-way switching valve 616. A gas-side end of the outdoor heat exchanger 612 is connected with a second port P2 of the four-way switching valve 616. A liquid-side end of the outdoor heat exchanger 612 is connected to a liquid-side end of the indoor heat exchanger 614 via the expansion valve 613. A gas-side end of the indoor heat exchanger 614 is connected to a third port P3 of the four-way switching valve 616. A fourth port P4 of the four-way switching valve 616 is connected to the suction side of the compressor 611.

The four-way switching valve 616 allows switching between a first communication state and a second communication state. In the first communication state (denoted by broken lines in the drawing), the first port P1 communicates with the second port P2, and the third port P3 communicates with the fourth port P4. In the second communication state (denoted by solid lines), the first port P1 communicates with the third port P3, and the second port P2 communicates with the fourth port P4. The direction in which refrigerant circulates may be reversed in accordance with the switching operation of the four-way switching valve 616.

In the third embodiment, the air-conditioning refrigerant circuit 615 is charged with refrigerant for the vapor compression refrigeration cycle. The refrigerant is a refrigerant mixture containing 1,2-difluoroethylene and may be any one of the refrigerants A to D mentioned above.

(25-3-2-2) Hot Water Supply Apparatus

The hot water supply apparatus 620 includes a hot-water-supply refrigerant circuit 625. The hot-water-supply refrigerant circuit 625 includes a compressor 621, a first heat exchanger 622, an expansion valve 623, and a second heat exchanger 624, which are serially connected to each other. The hot-water-supply refrigerant circuit 625 is charged with refrigerant, which is a carbon dioxide refrigerant. The devices constituting the hot-water-supply refrigerant circuit 625 and accommodated in a casing are incorporated into the hot water supply apparatus 620 to constitute a water supply unit.

The first heat exchanger 622 is a water-refrigerant heat exchanger, which is a combination of a heat absorbing unit 622 a and a heat radiating unit 622 b. The heat radiating unit 622 b of the first heat exchanger 622 is connected to the hot-water-supply refrigerant circuit 625, and the heat absorbing unit 622 a of the first heat exchanger 622 is connected to the hot-water-supply hot water circuit 640, in which water heating is performed to generate hot water. In the first heat exchanger 622, water heating is performed to generate hot water in the hot-water-supply hot water circuit 640 in such a manner that heat is exchanged between water in the hot-water-supply hot water circuit 640 and the carbon dioxide refrigerant in the hot-water-supply refrigerant circuit 625.

The hot-water-supply hot water circuit 640 is connected with a circulating pump 641, the heat absorbing unit 622 a of the first heat exchanger 622, and a hot water storage tank 642. The hot-water-supply hot water circuit 640 provides water-hot water circulation, where water receives heat from the carbon dioxide refrigerant in the first heat exchanger 622 and the generated hot water is then stored in the hot water storage tank 642. For water supply and drainage to and from the hot water storage tank 642, the hot-water-supply hot water circuit 640 is connected with a water supply pipe 643 leading to the hot water storage tank 642 and a hot water outflow pipe 644 leading from the hot water storage tank 642.

The second heat exchanger 624 is a cascade heat exchanger and is a combination of a heat absorbing unit 624 a and a heat radiating unit 624 b. The heat absorbing unit 624 a is connected to the hot-water-supply refrigerant circuit 625, and the heat radiating unit 624 b is connected to the air-conditioning refrigerant circuit 615. With the second heat exchanger 624 being a cascade heat exchanger, the air-conditioning refrigerant circuit 615 is in charge of operation on the low-stage (low-temperature) side of the two-stage heat pump cycle, and the hot-water-supply refrigerant circuit 625 is in charge of operation on the high-stage (high-temperature) side of the two-stage heat pump cycle.

The second heat exchanger 624 and the indoor heat exchanger 614 in the air-conditioning refrigerant circuit 615, which is the low-stage side of the two-stage heat pump cycle, are connected in parallel. A three-way switching valve 650 allows switching between the state in which refrigerant in the air-conditioning refrigerant circuit 615 flows through the second heat exchanger 624 and the state in which the refrigerant flows through the indoor heat exchanger 614. In other words, the air-conditioning refrigerant circuit 615, which is the low-stage side of the two-stage heat pump cycle, is capable of switching between a first operation and a second operation. During the first operation, refrigerant circulates between the outdoor heat exchanger 612 and the indoor heat exchanger 614. During the second operation, refrigerant circulates between the outdoor heat exchanger 612 and the second heat exchanger 624.

(25-3-3) Operation and Working of Air-Conditioning Hot Water Supply System

The following describes the operation and working of the air-conditioning hot water supply system 600.

Air conditioning operation that is the first operation may be performed in such a way as to switch between cooling operation and heating operation. During the cooling operation, the four-way switching valve 616 is set into the first communication state on the broken lines, and the three-way switching valve 650 is set into a first communication state on a broken line. In this setup, refrigerant discharged by the compressor 611 flows through the four-way switching valve 616, enters the outdoor heat exchanger 612 and is condensed in the outdoor heat exchanger 612 by transferring heat to outside air. The refrigerant is expanded in the expansion valve 613 and then enters the indoor heat exchanger 614, where the refrigerant evaporates by absorbing heat from room air. Consequently, the room air is cooled. The refrigerant then flows through the four-way switching valve 616 and is sucked into the compressor 611. The room is cooled by repeated cycles of a compression stroke, a condensation stroke, an expansion stroke, and an evaporation stroke while the refrigerant circulates as described above.

During the heating operation, the four-way switching valve 616 is set into the second communication state on the solid lines, and the three-way switching valve 650 is set into the first communication state on the broken line. In this setup, refrigerant discharged by the compressor 611 flows through the four-way switching valve 616 and the three-way switching valve 650, enters the indoor heat exchanger 614, and is condensed in the indoor heat exchanger 614 by transferring heat to room air. Consequently, the room air is heated. The refrigerant is expanded in the expansion valve 613 and then enters the outdoor heat exchanger 612, where the refrigerant evaporates by absorbing heat from outside air. The refrigerant then flows through the four-way switching valve 616 and is sucked into the compressor 611. The room is heated while the refrigerant circulates as described above.

Meanwhile, hot water storage operation that is the second operation is performed in the middle of the night when air conditioning is not needed. During this operation, the four-way switching valve 616 in the air-conditioning refrigerant circuit 615 is set into the second communication state on the solid lines as in the heating operation, and the three-way switching valve 650 in the air-conditioning refrigerant circuit 615 is set into a second communication state on a solid line as opposed to the state into which the three-way switching valve 650 is set during air conditioning operation. The compressor 621 in the hot-water-supply refrigerant circuit 625 and the circulating pump 641 in the hot-water-supply hot water circuit 640 are also operated.

In this setup, the air-conditioning refrigerant circuit 615 works as follows: refrigerant discharged by the compressor 611 flows through the four-way switching valve 616 and the three-way switching valve 650 and then enters the heat radiating unit 624 b of the second heat exchanger 624. In the heat radiating unit 624 b, refrigerant flowing through the air-conditioning refrigerant circuit 615 is condensed by transferring heat to the carbon dioxide refrigerant in the hot-water-supply refrigerant circuit 625. Consequently, the carbon dioxide refrigerant is heated. The refrigerant in the air-conditioning refrigerant circuit 615 is then expanded in the expansion valve 613, evaporates in the outdoor heat exchanger 612, flows through the four-way switching valve 616, and is sucked into the compressor 611. The refrigerant in the air-conditioning refrigerant circuit 615 circulates as described above to undergo repeated cycles of a compression stroke, a condensation stroke, an expansion stroke, and an evaporation stroke.

The carbon dioxide refrigerant in the hot-water-supply refrigerant circuit 625 undergoes a compression stroke in the compressor 621, a heat radiation stroke in the heat radiating unit 622 b of the first heat exchanger 622, an expansion stroke in the expansion valve 623, and a heat absorption stroke in the heat absorbing unit 624 a of the second heat exchanger 624 in the stated order. In the second heat exchanger 624, the carbon dioxide refrigerant absorbs heat from the refrigerant flowing through the air-conditioning refrigerant circuit 615. In the first heat exchanger 622, the carbon dioxide refrigerant transforms the warmth to water in the hot-water-supply hot water circuit 640.

In the hot-water-supply hot water circuit 640, the circulating pump 641 supplies water in the hot water storage tank 642 to the heat absorbing unit 622 a of the first heat exchanger 622, where the water is heated (hot water is generated). The hot water generated by the application of heat is sent back to the hot water storage tank 642 and continues to circulate through the hot-water-supply hot water circuit 640 until a predetermined thermal storage temperature is reached. As mentioned above, the hot water storage operation is performed in the middle of the night. Meanwhile, hot water supply operation for letting out hot water from the hot water storage tank 642 is performed during daytime or nighttime hours. During the hot water supply operation, the hot-water-supply refrigerant circuit 625 is nonoperational, and the indoor heat exchanger 614 in the air-conditioning refrigerant circuit 615 may be used to perform the cooling operation or the heating operation.

(25-3-4) Features of Air-Conditioning Hot Water Supply System

The air-conditioning hot water supply system 600 according to the third embodiment includes the hot water supply apparatus 620, which is a unit-type apparatus. This apparatus includes a cascade heat exchanger as the second heat exchanger 624 on the heat source side of the hot-water-supply refrigerant circuit 625, in which carbon dioxide is used as refrigerant. The second heat exchanger 624 is connected to the air-conditioning refrigerant circuit 615, which is a low-stage-side refrigerant circuit. This configuration enables two-stage heat pump cycle operation. The refrigerant used in the air-conditioning refrigerant circuit 615 is a refrigerant mixture containing 1,2-difluoroethylene and is any one of the refrigerants A to D mentioned above. These features enhance the efficiency of heat exchange in the second heat exchanger 624.

(25-3-5) Modification of Third Embodiment

In the embodiment above, the refrigerant mixture that is any one of the refrigerants A to D mentioned above is used as the first refrigerant sealed in the air-conditioning refrigerant circuit 615, which is the first cycle, and carbon dioxide is used as the second refrigerant sealed in the hot-water-supply refrigerant circuit 625, which is the second cycle. It is preferred that a refrigerant whose saturation pressure at a predetermined temperature is lower than the saturation pressure of the first refrigerant at the predetermined temperature be used as the second refrigerant sealed in the hot-water-supply refrigerant 625. For example, it is preferred that R134a be sealed in the hot-water-supply refrigerant circuit 625.

While the embodiments of the present disclosure have been described herein above, it is to be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure presently or hereafter claimed.

REFERENCE SIGNS LIST (1) Reference Signs of the Technique of First and Third Group of FIG. 3A to 3X

-   -   1, 1 a to 1 m air conditioning apparatus (refrigeration cycle         apparatus)     -   7 controller (control unit)     -   10 refrigerant circuit     -   20 outdoor unit     -   21 compressor     -   23 outdoor heat exchanger (condenser, evaporator)     -   24 outdoor expansion valve (decompressing section)     -   25 outdoor fan     -   26 indoor bridge circuit     -   27 outdoor-unit control unit (control unit)     -   30 indoor unit, first indoor unit     -   31 indoor heat exchanger, first indoor heat exchanger         (evaporator, condenser)     -   32 indoor fan, first indoor fan     -   33 indoor expansion valve, first indoor expansion valve         (decompressing section)     -   34 indoor-unit control unit, first indoor-unit control unit         (control unit)     -   35 second indoor unit     -   36 second indoor heat exchanger (evaporator, condenser)     -   37 second indoor fan     -   38 second indoor expansion valve (decompressing section)     -   39 second indoor-unit control unit (control unit)     -   40 bypass pipe     -   41 low-pressure receiver     -   42 high-pressure receiver     -   43 intermediate-pressure receiver     -   44 first outdoor expansion valve (decompressing section, first         decompressing section)     -   45 second outdoor expansion valve (decompressing section, second         decompressing section)     -   46 subcooling pipe     -   47 subcooling heat exchanger     -   48 subcooling expansion valve     -   49 bypass expansion valve     -   50 suction refrigerant heating section (refrigerant heat         exchanging section)     -   51 internal heat exchanger (refrigerant heat exchanging section)

(2) Reference Signs of the Technique of Thirteenth Group of FIG. 4A to 4K

-   -   1: air conditioner     -   21: rectifier circuit     -   22: capacitor     -   25: inverter     -   27: converter     -   30: power conversion device     -   30B: indirect matrix converter (power conversion device)     -   30C: matrix converter (power conversion device)     -   70: motor     -   71: rotor     -   100: compressor     -   130: power conversion device     -   130B: indirect matrix converter (power conversion device)     -   130C: matrix converter (power conversion device)

(3) Reference Signs of the Technique of Fourteenth Group of FIG. 5A to 5C

-   -   1: air conditioner     -   20: activation circuit     -   21: positive temperature coefficient thermistor     -   22: operation capacitor     -   30: connection unit     -   70: motor     -   90: single-phase AC power source     -   100: compressor     -   130: connection unit     -   170: motor     -   190: three-phase AC power source     -   200: compressor

(4) Reference Signs of the Technique of Fifteenth Group of FIG. 6A to 6N

-   -   1 warm-water supply system (warm-water generating apparatus)     -   1 a warm-water supply system (warm-water generating apparatus)     -   1 b warm-water supply system (warm-water generating apparatus)     -   21 compressor     -   22 water heat exchanger (second heat exchanger)     -   23 expansion valve (expansion mechanism)     -   24 air heat exchanger (first heat exchanger)     -   30 circulating water pipe (circulation flow path; second         circulation flow path)     -   30 b circulating water pipe (first circulation flow path)     -   35 warm-water storage tank (tank)     -   38 heat exchange section (part of first circulation flow path)     -   60 auxiliary circulating water pipe (first circulation flow         path)     -   62 auxiliary water heat exchanger (third heat exchanger)     -   110 water circulation pipe (second circulation flow path)     -   112 water heat exchanger (third heat exchanger)     -   118 flow path (third flow path)     -   211 compressor     -   212 radiator (second heat exchanger)     -   213 expansion valve (expansion mechanism)     -   214 evaporator (second heat exchanger)     -   231 pipe (first circulation flow path)     -   240 tank     -   241 flow path (second flow path)     -   241 a warm-water supply heat exchanger (part of second flow         path)     -   320 water receiving tank (water supply source)     -   312 water supply line (flow path)     -   314 warm-water exit line (flow path)     -   331 water flow path (flow path)     -   333 second heat exchanger     -   335 compressor     -   336 expansion valve (expansion mechanism)     -   337 first heat exchanger     -   340 warm-water storage tank (tank)

(5) Reference Signs of the Technique of Seventeenth Group of FIG. 7A to 7O

-   -   1, 601, 701 air conditioning apparatus     -   2 indoor unit (example of use-side unit)     -   3 outdoor unit (example of heat-source-side unit)     -   209, 721 first duct     -   210, 722 second duct     -   230, 621, 730 casing     -   242 indoor heat exchanger (example of use-side heat exchanger)     -   321, 633, 741 compressor     -   323, 634 outdoor heat exchanger (example of heat-source-side         heat exchanger)     -   602 use-side unit     -   603 heat-source-side unit     -   625 air supply heat exchanger (example of use-side heat         exchanger)     -   651 air supply duct (example of first duct)     -   653 suction duct (example of third duct)     -   739 partition plate     -   743 heat-source-side heat exchanger     -   745 use-side heat exchanger

(6) Reference Signs of the Technique of Twenty-Second Group of FIG. 8A to 8J

-   -   10 refrigeration cycle apparatus     -   11, 110 refrigerant circuit     -   12, 122 compressor     -   13, 123 heat source-side heat exchanger     -   14 expansion mechanism     -   15 usage-side heat exchanger     -   100, 10 a air conditioning apparatus (refrigeration cycle         apparatus)     -   124 heat source-side expansion mechanism (expansion mechanism)     -   131 usage-side heat exchanger, first usage-side heat exchanger         (usage-side heat exchanger)     -   133 usage-side expansion mechanism, first usage-side expansion         mechanism (expansion mechanism)     -   136 second usage-side heat exchanger (usage-side heat exchanger)     -   138 second usage-side expansion mechanism (expansion mechanism)

(7) Reference Signs of the Technique of Twenty-Fifth Group of FIG. 9A to 9E

-   -   11 compressor (first compressor)     -   14 heat-source-side heat exchanger (first radiator)     -   31 expansion valve (first expansion mechanism)     -   33 heat exchanger     -   60 use-side unit (second heat absorber)     -   100 heat load treatment system (refrigeration apparatus)     -   500 two-stage refrigeration apparatus (refrigeration apparatus)     -   510 first cycle     -   511 first compressor     -   512 first condenser (first radiator)     -   513 first expansion valve (first expansion mechanism)     -   514 first evaporator (first heat absorber)     -   520 second cycle     -   521 second compressor     -   523 second downstream-side condenser (second radiator)     -   524 second upstream-side expansion valve (second expansion         mechanism)     -   526 second downstream-side expansion valve (second expansion         mechanism)     -   527 second evaporator (second heat absorber)     -   531 cascade condenser (heat exchanger)     -   HC heat medium circuit (second cycle)     -   HP heat medium path in heat exchanger (second radiator)     -   RC refrigerant circuit (first cycle)     -   RP refrigerant path in heat exchanger (first heat absorber)     -   600 air-conditioning hot water supply system (refrigeration         apparatus)     -   611 compressor (first compressor)     -   612 outdoor heat exchanger (first heat absorber)     -   613 expansion valve (first expansion mechanism)     -   615 air-conditioning refrigerant circuit (first cycle)     -   621 compressor (second compressor)     -   622 b heat radiating unit (second radiator)     -   623 expansion valve (second expansion mechanism)     -   624 second heat exchanger (heat exchanger)     -   624 a heat absorbing unit (second heat absorber)     -   624 b heat radiating unit (first radiator)     -   625 hot-water-supply refrigerant circuit (second cycle)

CITATION LIST Patent Literature

PTL 1: International Publication No. 2015/141678 

1. A refrigeration cycle apparatus comprising: a refrigerant circuit including a compressor, a condenser, a decompressing section, and an evaporator; and a refrigerant containing at least 1,2-difluoroethylene enclosed in the refrigerant circuit.
 2. The refrigeration cycle apparatus according to claim 1, wherein the refrigerant comprises trans-1,2-difluoroethylene (HFO-1132 (E)), trifluoroethylene (HFO-1123), and 2,3,3,3-tetrafluoro-1-propene (R1234yf).
 3. The refrigeration cycle apparatus according to claim 2, wherein when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments OD, DG, GH, and HO that connect the following 4 points: point D (87.6, 0.0, 12.4), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point O (100.0, 0.0, 0.0), or on the line segments OD, DG, and GH (excluding the points O and H); the line segment DG is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402), the line segment GH is represented by coordinates (−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and the line segments HO and OD are straight lines.
 4. The refrigeration cycle apparatus according to claim 2, wherein when the mass % of HFO-1132(E), HFO-1123, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments LG, GH, HI, and IL that connect the following 4 points: point L (72.5, 10.2, 17.3), point G (18.2, 55.1, 26.7), point H (56.7, 43.3, 0.0), and point I (72.5, 27.5, 0.0), or on the line segments LG, GH, and IL (excluding the points H and I); the line segment LG is represented by coordinates (0.0047y²−1.5177y+87.598, y, −0.0047y²+0.5177y+12.402), the line segment GH is represented by coordinates (−0.0134z²−1.0825z+56.692, 0.0134z²+0.0825z+43.308, z), and the line segments HI and IL are straight lines.
 5. The refrigeration cycle apparatus according to claim 2, further comprising difluoromethane (R32).
 6. The refrigeration cycle apparatus according to claim 5, wherein when the mass % of HFO-1132(E), HFO-1123, R1234yf, and R32 based on their sum in the refrigerant is respectively represented by x, y, z, and a, if 0<a≤10.0, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R1234yf is 100 mass % are within the range of a figure surrounded by straight lines that connect the following 4 points: point A (0.02a²−2.46a+93.4, 0, −0.02a²+2.46a+6.6), point B′ (−0.008a²−1.38a+56, 0.018a²−0.53a+26.3, −0.01a²+1.91a+17.7), point C (−0.016a²+1.02a+77.6, 0.016a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point O and point C); if 10.0<a≤16.5, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points: point A (0.0244a²−2.5695a+94.056, 0, −0.0244a²+2.5695a+5.944), point B′ (0.1161a²−1.9959a+59.749, 0.014a²−0.3399a+24.8, −0.1301a²+2.3358a+15.451), point C (−0.0161a²+1.02a+77.6, 0.0161a²−1.02a+22.4, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point O and point C); or if 16.5<a≤21.8, coordinates (x,y,z) in the ternary composition diagram are within the range of a figure surrounded by straight lines that connect the following 4 points: point A (0.0161a²−2.3535a+92.742, 0, −0.0161a²+2.3535a+7.258), point B′ (−0.0435a²−0.0435a+50.406, −0.0304a²+1.8991a−0.0661, 0.0739a²−1.8556a+49.6601), point C (−0.0161a²+0.9959a+77.851, 0.0161a²−0.9959a+22.149, 0), and point O (100.0, 0.0, 0.0), or on the straight lines OA, AB′, and B′C (excluding point O and point C).
 7. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132 (E)), trifluoroethylene (HFO-1123) in a total amount of 99.5 mass % or more based on the entire refrigerant, and the refrigerant comprising 62.5 mass % to 72.5 mass % of HFO-1132(E) based on the entire refrigerant.
 8. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), difluoromethane (R32), and 2,3,3,3-tetrafluoro-1-propene (R1234yf), wherein when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AC, CF, FD, and DA that connect the following 4 points: point A (71.1, 0.0, 28.9), point C (36.5, 18.2, 45.3), point F (47.6, 18.3, 34.1), and point D (72.0, 0.0, 28.0), or on these line segments; the line segment AC is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+28.904), the line segment FD is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and the line segments CF and DA are straight lines.
 9. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), difluoromethane (R32), and 2,3,3,3-tetrafluoro-1-propene (R1234yf), wherein when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments AB, BE, ED, and DA that connect the following 4 points: point A (71.1, 0.0, 28.9), point B (42.6, 14.5, 42.9), point E (51.4, 14.6, 34.0), and point D (72.0, 0.0, 28.0), or on these line segments; the line segment AB is represented by coordinates (0.0181y²−2.2288y+71.096, y, −0.0181y²+1.2288y+28.904), the line segment ED is represented by coordinates (0.02y²−1.7y+72, y, −0.02y²+0.7y+28), and the line segments BE and DA are straight lines.
 10. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), difluoromethane (R32), and 2,3,3,3-tetrafluoro-1-propene (R1234yf), wherein when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GI, IJ, and JG that connect the following 3 points: point G (77.5, 6.9, 15.6), point I (55.1, 18.3, 26.6), and point J (77.5, 18.4, 4.1), or on these line segments; the line segment GI is represented by coordinates (0.02y²−2.4583y+93.396, y, −0.02y²+1.4583y+6.604), and the line segments IJ and JG are straight lines.
 11. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), difluoromethane (R32), and 2,3,3,3-tetrafluoro-1-propene (R1234yf), wherein when the mass % of HFO-1132(E), R32, and R1234yf based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), R32, and R1234yf is 100 mass % are within the range of a figure surrounded by line segments GH, HK, and KG that connect the following 3 points: point G (77.5, 6.9, 15.6), point H (61.8, 14.6, 23.6), and point K (77.5, 14.6, 7.9), or on these line segments; the line segment GH is represented by coordinates (0.02y²−2.4583y+93.396, y, −0.02y²+1.4583y+6.604), and the line segments HK and KG are straight lines.
 12. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and difluoromethane (R32), wherein when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′E′, E′A′, and A′O that connect the following 5 points: point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), point E′ (41.8, 39.8, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments C′D′, D′E′, and E′A′ (excluding the points C′ and A′); the line segment C′D′ is represented by coordinates (−0.0297z²−0.1915z+56.7, 0.0297z²+1.1915z+43.3, z), the line segment D′E′ is represented by coordinates (−0.0535z²+0.3229z+53.957, 0.0535z²+0.6771z+46.043, z), and the line segments OC′, E′A′, and A′O are straight lines.
 13. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and difluoromethane (R32), wherein when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC, CD, DE, EA′, and A′O that connect the following 5 points: point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), point E (72.2, 9.4, 18.4), and point A′ (81.6, 0.0, 18.4), or on the line segments CD, DE, and EA′ (excluding the points C and A′); the line segment CDE is represented by coordinates (−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and the line segments OC, EA′, and A′O are straight lines.
 14. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and difluoromethane (R32), wherein when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC′, C′D′, D′A, and AO that connect the following points: point O (100.0, 0.0, 0.0), point C′ (56.7, 43.3, 0.0), point D′ (52.2, 38.3, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments C′D′ and D′A (excluding the points C′ and A); the line segment C′D′ is represented by coordinates (−0.0297z²−0.1915z+56.7, 0.0297z²+1.1915z+43.3, z), and the line segments OC′, D′A, and AO are straight lines.
 15. The refrigeration cycle apparatus according to claim 1, the refrigerant comprising trans-1,2-difluoroethylene (HFO-1132(E)), trifluoroethylene (HFO-1123), and difluoromethane (R32), wherein when the mass % of HFO-1132(E), HFO-1123, and R32 based on their sum in the refrigerant is respectively represented by x, y, and z, coordinates (x,y,z) in a ternary composition diagram in which the sum of HFO-1132(E), HFO-1123, and R32 is 100 mass % are within the range of a figure surrounded by line segments OC, CD, DA, and AO that connect the following points: point O (100.0, 0.0, 0.0), point C (77.7, 22.3, 0.0), point D (76.3, 14.2, 9.5), and point A (90.5, 0.0, 9.5), or on the line segments CD and DA (excluding the points C and A); the line segment CD is represented by coordinates (−0.017z²+0.0148z+77.684, 0.017z²+0.9852z+22.316, z), and the line segments OC, DA, and AO are straight lines. 